Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (2024)

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Caramelized Onion Puff Pastry Bites with sautéed crimini mushrooms, balsamic caramelized onions, and applewood smoked gruyere cheese. The perfect little appetizers! They’re made with puff pastry and take no time at all to whip up. They are the perfect appetizers to serve your guests this holiday season!

Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (1)

Snappetizers!

Buttery, flaky puff pastry topped with balsamic caramelized onions, sauteéd mushrooms, a hint of garlic, and a smoked gruyere cheese bomb mixed right in.

These caramelized onion bites are a game-changer for me. They’re perfect to serve your Thanksgiving, Christmas, and New Years guests before a big dinner. Also, they totally look fancy schmancy, but nobody really needs to know that the caramelized onion and sauteéd mushroom filling can be made a couple of days ahead of time.

I’ve had readers tell me that these easy caramelized onion puff pastry bites flew out of the oven and right onto the guests’ plates! They are always a hit when we make them for parties, and with a sprinkle of parsley or some fresh thyme, the scent of these caramelized onion bites is UNREAL.

How to make caramelized onion bites:

Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (2)

Ingredients for caramelized onion tarts (or tartlets)

  • Butter and oil:We’ll use these ingredients to saute the mushrooms and the onions for the recipe. I like to use a high-heat oil such as avocado, sunflower, or vegetable to cook the onions and mushrooms.
  • Mushrooms:I prefer to use small crimini or baby bella mushrooms, but button mushrooms, shiitakes, or a medley of mushrooms would also work for this recipe.
  • Yellow onions:slice the onions thinly so that the caramelizes quicker in the pan. We’ll cook them down in a large skillet until they are tender and delicious.
  • Dried or fresh thyme:We’ll use some type to flavor the onions.
  • Seasonings:I keep things pretty simple. You’ll want some sugar to help the caramelization process of the onions; you’ll also need kosher salt, black pepper, and some garlic powder.
  • Balsamic Vinegar:The syrupy vinegar cooks down with the onions and creates a balsamic glaze in the pan. This not only gives the onions a more delicious color, it also helps boost the sweetness which pairs beautifully with the nutty gruyere cheese.
  • Gruyere Cheese:I like to use applewood smoked gruyere for this recipe as the smoky flavor pairs well with the sweetness of the jammy onions and the natural umami or mushrooms. You can also use regular gruyere or other economical options like white cheddar.
  • Puff Pastry:For this recipe, you’ll need a box of frozen puff pastry. To make the process smoother, I like to thaw the puff pastry in the refrigerator overnight according to the package directions. I’ve never been able to get puff pastry to defrost quickly, so definitely plan ahead for this recipe.
  • Large egg:This is for the egg wash! It just gives the puff pastry a beautiful sheen when it comes out of the oven.
Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (3)
Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (4)

How to make caramelized onion puff pastry bites:

  1. Start with the mushrooms.We’re going to start by sautéing the mushrooms in a few tablespoons of oil for 4-5 minutes. Once they start to brown, remove them to small bowl.
  2. Caramelize the onions.Add the remaining butter to the pan. Once it melts, add the onions. Let them hang out in the pan for 5 minutes. Remember to use a cast iron or stainless steel skillet. You also want to avoid using a nonstick skillet as the onions won’t caramelize. After the 5 minutes, season ith sugar and thyme. Now crank the heat down to about medium-low, and cook for a total of 25 minutes. Keep checking on them every 5-10 minutes, and give them a stir to keep them from browning too quickly. Drizzle the balsamic to help deglaze the pan, and when it’s all been soaked up, you can turn off the stove. Once the onions have cooled slightly, add them to the mushrooms and season with a little garlic powder, salt, and pepper.
  3. Store or use right away.Let your filling come to room temperature, you can store it in an air-tight container for up to 48 hours in the refrigerator. If you decide to make the filling ahead of time, zap it in the microwave to bring it back to room temp before continuing with the recipe instructions. Mix in the gruyere cheese and combine well.
  4. Make the bites.Cut the puff pastry sheet into small squares or rectangles using a pizza cutter or a sharp knife. I cut mine into 2-inch squares. Lay a piece of parchment paper on a large baking sheet. Place the squares on the prepared sheet pan. Brush them with a beaten egg using a pastry brush. Drop about a tablespoon of caramelized onion mixture on each puff pastry square.
  5. Bake:bake the caramelized onion puff pastry bites in the preheated oven until they are crisp and golden brown. Let them cool slightly before serving. Top with fresh parsley or thyme for a little color!
Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (5)
Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (6)

Look at each of those puff pastry layers and how perfectly they separate from each other. It’s like taking a bite out of 10 potato chips at the same time, only less crunchy, and more buttery. Okay, so not like a potato chip at all, really.

Caramelized onion puff pastry bites are going to make your holidays more amazing. The garlic, the mushrooms, the caramelized onions, and the smoky gruyere.

If you like this caramelized onion bites recipe, you might also like:

  • Chicken Puff Pastry (Chicken Patties)
  • Easy Puff Pastry Twists with Za’atar
  • Crispy Feta Cheese Filo Pastry Spirals
  • Greek Spinach Puffs
  • Hot Honey Cranberry Goat Cheese Balls
Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (7)

Yield: makes 30-34 bites

Caramelized Onion Puff Pastry Bites with Gruyere and Mushrooms

Prep Time15 minutes

Cook Time45 minutes

Total Time1 hour

Caramelized Onion Puff Pastry bites with sautéed crimini mushrooms, balsamic caramelized onions, and applewood smoked gruyere cheese. The perfect little appetizers! They’re made with puff pastry and take no time at all to whip up! These are the perfect appetizers to serve your guests this holiday season.

Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (8)

Ingredients

  • 4 tablespoons salted butter, divided
  • 2 tablespoons vegetable oil, divided
  • 5-6 ounces crimini or button mushrooms, sliced
  • 2 medium yellow onions, thinly sliced
  • 1/4 teaspoon dried thyme
  • 1 tablespoon sugar
  • 1 1/2 tablespoon balsamic vinegar
  • 1/4 teaspoon garlic powder
  • salt and pepper, to taste
  • 4 ounces grated gruyere cheese (I used applewood smoked gruyere)
  • 1 package (1 pound) frozen puff pastry, thawed
  • 1 egg, lightly beaten

Instructions

  1. MUSHROOMS: In a large cast iron skillet over medium heat, heat 1 tablespoon of oil along with 1 tablespoon of butter. When the butter melts, add the mushrooms and sauté for about 5 minutes until golden and tender. Remove and set aside in a medium bowl.
  2. CARAMELIZE: Heat the remaining 3 tablespoons of butter along with 1 tablespoon of oil and sauté the onions for 5 minutes. Add the dried thyme and sugar and continue to cook for 25 minutes on medium-low heat. Make sure to stir the mixture every 5-10 minutes. If the onions are caramelizing too fast, turn down the heat a little more.
  3. DEGLAZE: Add the balsamic vinegar to deglaze the pan, allow the onions to soak it all in. Turn off heat. Add the onions to the mushroom mixture. Season with the garlic powder and salt and pepper to taste, stir to combine.
  4. MAKE AHEAD: Allow to cool to room temperature. The mixture can be kept in an air-tight container in the fridge for up to 48 hours. Allow to come to room temperature before proceeding. Add the gruyere cheese and mix well.
  5. PREP FOR BAKING: Position two racks in the upper and lower thirds of the oven. Preheat the oven to 400º F. Line 2 baking sheets with parchment paper or silicone mats.
  6. FILL: Using a sharp knife or a pizza cutter, cut the puff pastry into 2-inch squares and place them on a lined baking sheet. Make sure the puff pastry is cold before proceeding. If not, allow it to rest in the refrigerator for 10-15 minutes before proceeding. Using a pastry brush, brush the beaten egg on the squares. Prick the puff pastry using a fork in the center. Place a tablespoon of caramelized onion mixture in the center.
  7. BAKE: for 20-25 minutes, rotating the pan halfway in between until crisp and golden brown. Let cool slightly before serving.

Notes

  • Make sure the puff pastry is cold when it goes into the oven. If at any point it becomes soft, allow it to rest in the refrigerator for 15-20 minutes or until it firms up again. Do not open the oven door during the first 10 minutes of baking time. Frequently opening the oven may cause the puff pastry to not 'puff up'.
  • Mozzarella or gouda cheese may be used to replace the gruyere. I really like the smoky flavor of applewood smoked gruyere with these bites.
  • If you've prepared the caramelized onion mixture ahead of time, you can zap it in the microwave for 30 seconds to bring it back to room temperature quickly.

Have you made this recipe?

If you enjoyed this recipe, please consider leaving a ⭐️⭐️⭐️⭐️⭐️ rating and a comment below. You can also share a picture on Instagram with the hashtag #LITTLESPICEJAR, I'd love to see what you made!

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originally published on Dec 8, 2014 (last updated Dec 18, 2023)

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115 comments on “Caramelized Onion Puff Pastry Bites with Gruyere and Mushrooms”

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  1. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (9)

    hipfoodiemom Reply

    I make a tart just like this . . but love your idea of pre-cutting the puff pastry. . so beautiful and yes, a great appetizer for the holidays!

  2. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (10)

    Winnie Reply

    I tried making this recipe and followed the instructions on the store bought puff pastry box to the T but the puff pastry was too puffy! Do I need to roll it out a bit? What did I do wrong?

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (11)

      Marzia Reply

      Hi Winnie, for next time, i’d suggest scoring a ¼ inch border on the puff pastry (and place the onion mushroom mixture inside the borders) this should keep the pastry from puffing up too much. You could even use a fork and just pierce holes all over the unbaked puff pastry squares before adding the pastry on top and baking. Either method would work. It’s really nothing you did, the brand of puff pastry you used just happened to be extra puffy 🙂

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (12)

      Laura Reply

      Since my bf became vegetarian we looked for something that tastes like Christmas and for 5 years now it has been this recipe. The only difference is I use brie cheese instead. What a great recipe! Thank you for all the joy it has brought.

      5

  3. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (13)

    Heather Reply

    Ok–I tried to make this for a holiday party and they didn’t puff and were so tiny. Any idea what happened?

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (14)

      Marzia Reply

      Hi Heather,
      Hmmm. Did you perhaps open the oven door during the first 10 minutes of baking time? Sometimes, the puff pastry doesn’t rise if the oven temperature falls too much before the puff pastry has a chance to start puffing up. It could also be that the puff pastry wasn’t cold enough when it went into the oven. If the kitchen is super warm or if you live in a warm climate, the puff pastry sheets sometimes need a few minutes in the refrigerator before going into the oven. I’ll also add these as notes into the recipe, thanks for your feedback.

  4. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (15)

    Paul Reply

    Greetings Marzia, Great recipe. I’m doing this for our Christmas gathering. I noticed the pictures included a green well sliced leaf. Is that parsley?

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (16)

      Marzia Reply

      Hi Paul! Yes, that’s parsley. 🙂 Just sprinkled some on to make it look a little more attractive for pictures!

  5. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (17)

    Kim Hermann Reply

    I made a double batch of these last night for a party. They were wonderful and a big hit! There were a handful left over and I heated them on low in the oven and topped them with basic scrambled eggs with cheese and tomatoes. Also delicious!

  6. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (18)

    SARA Reply

    Maybe I’m missing it but when do you add garlic powder and salt and pepper?

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (19)

      Marzia Reply

      Sara, you add the garlic powder, salt, and pepper after you combine the caramelized onions and mushrooms in a bowl.

  7. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (20)

    youmen Reply

    hi,just did it today….I mixed the mushrooms with emmenthal cheese . They were ok but the cheese was in a way like overcooked before the pastries puffed properly..so i had to add little bit of cheese as a topping and left it few seconds to melt

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (21)

      Marzia Reply

      The recipe specifically calls for gruyere, and although emmental cheese is similar, it’s always best to use the ingredients i’ve tested the recipe with. If you change the ingredients or quantities, it changes the recipe. Emmenthal cheese contains less fat than gruyere, perhaps this is why the ingredient didn’t work as a good substitute.

  8. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (22)

    Tricia Reply

    Made these for Valentine’s Day. Used a heart cookie cutter for the pasty dough and they turned out perfectly! This recipe is a winner for sure!
    Wish I could share a picture, so happy with how this turned out.

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (23)

      Connie Reply

      Great idea! I am making these for Christmas and will try using a large star cookie cutter!
      Thanks so much for the recipe!

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  13. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (24)

    EMB Reply

    These were great. However, having made these and french onion soup numerous times, you underestimate the time to properly caramelize onions. That creamy deep brown (but not burnt) texture takes at least twice what you listed (mine took an hour in a large cast iron). Not a deal-breaker, but certainly not a quick appetizer.

  14. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (25)

    Christina Reply

    I made these on Saturday night for a small dinner party and they were a tremendous hit! Followed your recipe exactly but use the mission fig balsamic vinegar instead of regular balsamic; so delicious!

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  20. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (26)

    Claire Reply

    I have made these a couple times now. Always a big hit. I have made them with and without mushrooms. I cut the puff pastry into 16 equal squares. I do not add any garlic, balsamic vinegar or sugar. Just onions cooked down in the oil/butter/salt topped with gruyere. They cook perfectly every time and are simple, elegant and delicious. You really only need 3 ingredients which is amazing!!

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  23. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (27)

    Kari wooten straach Reply

    So did I miss something or when do you add the cheese? I can’t wait to try this recipe for aChristmas party we are attending this coming weekend and I’m getting my shopping list made out. Just re-read and I still missed the chees step??!!! Thanks for your input!!!

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (28)

      Marzia Reply

      At the very bottom, in step #2 🙂

  24. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (29)

    Nancy@Seasonsofjoy Reply

    Delicious! People at the party I went to loved these! I thought I had the right cheese on hand, but I had Gouda, and they turned out wonderful!

    5

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  26. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (30)

    Jeannie Reply

    Can this recipe be made ahead of time and then frozen?

    • Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (31)

      Marzia Reply

      I’ve never tried freezing it so I really couldn’t say!

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  28. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (32)

    Laura Reply

    Really wonderful recipe! I took this to Christmas dinner after a friend gave me a bag of wild mushrooms. Just lovely. This dish travels well because you can keep the mushroom mixture separate from the puff pastry and then assemble and heat them for just a few minutes before serving. I may try this with sherry sometime too.

    5

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  30. Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (33)

    Amanda Reply

    I’ve made these at least three times in the last 2 months they are sooooo good! Simple easy too and they are so impressive. My puff pastry didn’t really fully puff in the past (still tasty) but this time I had been using the oven before I put them in, 425 roasting potatoes, and they are significantly more “puffed.” I
    did turn down to 400 before putting them in, but the hot oven made a difference. I also didn’t have parchment and used foil, rubbed butter all over it. Worked great. Thank you for the great recipe!!!

Caramelized Onion Puff Pastry Bites Recipe | Little Spice Jar (2024)
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