Description
These Caramelized Onion, Mushroom, Apple & Gruyère Bites are elegant and flavorful appetizers. Flaky puff pastry squares are topped with a savory-sweet mixture of caramelized onions, sautéed mushrooms, tender apples, and nutty Gruyère cheese, then baked until golden brown.
Ingredients
- 2 tablespoons vegetable oil (or canola oil)
- 1 large yellow onion, thinly sliced
- 4 ounces (113g) baby bella mushrooms, sliced
- 2 tablespoons (28g) unsalted butter
- 1 1/2 Granny Smith apples, peeled, cored, and cubed into 1/2-inch pieces
- 1 teaspoon granulated sugar
- 1 1/2 ounces (43g) Gruyère cheese, shredded (about 1/2 cup)
- 2 tablespoons fresh chives, minced
- 1/2 teaspoon dried thyme
- 1 pound (454g) frozen puff pastry, thawed according to package directions (usually two sheets)
- 1 large egg, beaten
- Salt
- Pepper
Instructions
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Preheat Oven and Prepare Baking Sheets: Preheat your oven to 400°F (200°C). Line two large baking sheets with silicone baking mats (Silpats) or parchment paper.
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Caramelize Onions: Heat the vegetable oil in a large skillet over medium heat. Add the thinly sliced onion and 1 teaspoon of salt. Cook, stirring occasionally, until the onions are deeply caramelized and a rich golden brown, about 30-35 minutes. This step takes time, but it’s crucial for developing the flavor of the filling. Reduce the heat if the onions start to burn. Remove the caramelized onions from the skillet and set them aside in a large bowl.
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Sauté Mushrooms: In the same skillet (no need to clean it), add the sliced mushrooms. Cook, stirring occasionally, until they are tender and have released their liquid, about 5 minutes. Remove the mushrooms from the skillet and add them to the bowl with the caramelized onions.
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Cook Apples: In the same skillet, melt the butter over medium heat. Add the cubed apples and the granulated sugar. Cook, stirring occasionally, until the apples are softened but still hold their shape, about 10 minutes. Remove from heat and add the cooked apples to the bowl with the onions and mushrooms.
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Combine Filling: Add the shredded Gruyère cheese, minced chives, and dried thyme to the bowl with the cooked onions, mushrooms, and apples. Stir gently to combine all the ingredients. Season the filling with salt and pepper to taste.
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Prepare Puff Pastry: Unfold the thawed puff pastry sheets on a lightly floured surface.
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Cut Puff Pastry: Using a pizza cutter or a sharp knife, cut each puff pastry sheet into 2-inch squares.
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Arrange on Baking Sheets: Place the puff pastry squares on the prepared baking sheets, leaving a little space between each square.
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Egg Wash: Brush the tops of the puff pastry squares with the beaten egg.
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Add Filling: Place a spoonful (about 1-2 teaspoons) of the filling in the center of each puff pastry square. Do not overfill.
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Bake: Bake for 25 minutes, rotating the baking sheets halfway through and switching their positions (top rack to bottom rack, and vice versa) to ensure even browning. The puff pastry should be golden brown and puffed, and the filling should be heated through.
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Cool and Serve: Let the tarts cool slightly on the baking sheets before serving. Serve warm.
Notes
- Puff Pastry: Make sure your puff pastry is thawed but still cold for easier handling. Follow the package directions for thawing.
- Onions: Caramelizing the onions slowly develops their sweetness and depth of flavor.
- Mushrooms: Baby bella mushrooms are recommended, but you can use other types of mushrooms, such as cremini or white button mushrooms.
- Apples: Granny Smith apples are used for their tartness, which balances the sweetness of the onions and the richness of the cheese. You can substitute other tart apples, such as Braeburn or Honeycrisp.
- Gruyère Cheese: Gruyère cheese has a nutty, slightly salty flavor that complements the other ingredients. You can substitute other cheeses, such as Swiss, Emmental, or Comté.
- Make-Ahead: You can prepare the filling ahead of time and store it in the refrigerator for up to 2 days. You can also assemble the bites (without the egg wash) and freeze them on a baking sheet, then transfer them to a freezer-safe bag. Bake from frozen, adding a few minutes to the baking time.
- Storage: store leftover bites.