Dessert

Mushroom and Caramelized Onion Puff Pastry Bites Recipe

ByRita Bennet December 22, 2025December 22, 2025

Introduction

Mushroom Puff Pastry Bites are a delightful appetizer featuring caramelized onions, savory mushrooms, and melted Gruyere tucked inside crispy puff pastry rounds. Perfect for parties or an elegant snack, these bites combine rich flavors with flaky texture.

Rows of small round puff pastry bites sit on a paper-lined white marbled surface, each made of two layers: a golden brown flaky pastry base topped with caramelized dark brown mushrooms sprinkled with bright green chopped herbs. The pastries have a soft shiny texture with some cheese melted between the layers, adding a creamy touch under the mushrooms. The arrangement is close and even, showing the puffiness and careful topping of each piece. photo taken with an iphone --ar 4:5 --v 7

Ingredients

2 tablespoons extra virgin olive oil (divided)
1 large yellow onion (thinly sliced)

1/2 teaspoon kosher salt
16 ounces baby bella mushrooms (sliced)

1/2 teaspoon minced garlic
2 teaspoons finely chopped fresh thyme leaves (or 1/2 teaspoon dried)

1/4 teaspoon ground black pepper
1/2 cup shredded Gruyere (Swiss, or similar cheese, about 1 1/2 ounces)
2, 10-inch square sheets frozen puff pastry (thawed)

1 egg (beaten)
3 tablespoons whole-grain mustard
Chopped fresh parsley (for garnish)

Instructions

Step 1: Place racks in the upper and lower thirds of your oven and preheat it to 400 degrees F. Line two large baking sheets with silicone baking mats or parchment paper. Set aside.
Step 2: In a large skillet over medium-low heat, warm 1 tablespoon of olive oil. Add the sliced onions and kosher salt. Sauté until the onions begin to brown, then reduce the heat to low and continue cooking, stirring occasionally, until they are deeply golden and caramelized, about 25 minutes. Transfer the onions to a large bowl and set aside.
Step 3: In the same skillet, heat the remaining tablespoon of olive oil over medium-low heat. Add the sliced mushrooms and sauté until tender, about 5 minutes. Stir in the minced garlic, thyme, and black pepper, and cook for another minute. Add the mixture to the bowl with the caramelized onions, then stir in the shredded cheese.

Step 4: On a lightly floured work surface, roll out one sheet of puff pastry to a 10.5-inch square. Using a 2-inch round cookie or biscuit cutter, cut the pastry into approximately 25 rounds. Repeat with the second sheet if desired, or keep for another use.
Step 5: Transfer the pastry rounds to the prepared baking sheets. Lightly brush each round with the beaten egg and prick gently with a fork to allow air to escape. Spread about 1/4 teaspoon whole grain mustard on each round, then top with about 1 tablespoon of the mushroom and onion filling.
Step 6: Bake for 25 minutes, rotating the pans 180 degrees and swapping their positions between the upper and lower racks halfway through baking. The pastry should be golden and crisp when done. Allow the bites to cool for 5 minutes before garnishing with chopped fresh parsley.

Tips & Variations

To keep the puff pastry from shrinking, chill it briefly after cutting and before baking.
Try adding a sprinkle of grated Parmesan for extra sharpness.
Substitute thyme with fresh rosemary or sage for a different herbal note.

Use a square cutter for less pastry waste and easier filling placement.

Storage

Store any leftover bites in an airtight container in the refrigerator for up to 3 days. Reheat gently in a 350°F oven for 5–7 minutes to regain crispiness. These bites are best enjoyed warm or at room temperature.

How to Serve

Small round puff pastry bites form the base layer, golden brown and flaky with visible layers. On top of each pastry is a melted cheese layer, light yellow with a slightly bubbly texture. Each bite has a thick, dark brown cooked mushroom slice layered over the cheese, with some mushrooms showing a slight crisp around the edges. Bright green chopped herbs are scattered atop each mushroom, adding a fresh contrast. All the bites are arranged closely together on a white marbled surface. Photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I prepare the filling ahead of time?

Yes, the mushroom and onion filling can be made a day in advance and stored in the refrigerator. Bring to room temperature before assembling the bites.