Caramelized Onion, Mushroom, Apple & Gruyere Bites (Elegant & Flavorful Appetizers!)

These Caramelized Onion, Mushroom, Apple & Gruyere Bites are the perfect combination of sweet, savory, and sophisticated flavors, all nestled in a flaky puff pastry crust! I love how these bite-sized appetizers are both elegant and easy to make. The caramelized onions, sautéed mushrooms, and sweet-tart apples complement the nutty Gruyere cheese beautifully. They’re perfect for holiday gatherings, parties, or any time you want to impress your guests with a delicious and impressive appetizer.

Why You’ll Love These Appetizer Bites

• Elegant and Flavorful: The combination of caramelized onions, mushrooms, apples, and Gruyere cheese creates a complex and delicious flavor profile.
• Flaky Puff Pastry: Using puff pastry makes these bites incredibly easy to make and creates a light, flaky crust.
• Perfect for Parties: These bites are a great appetizer for holiday gatherings, parties, or any special occasion.
• Make-Ahead Friendly: You can prepare the filling and even assemble the bites ahead of time.
• Customizable: You can easily adjust the ingredients to your liking.

Ingredients for Caramelized Onion, Mushroom, Apple & Gruyere Bites

Here’s what you’ll need to make these elegant appetizers. The full list with measurements is in the recipe card below.

Main Ingredients

• Vegetable oil (Oil)
• Large onion, thinly sliced (Vegetable)
• Baby bella mushrooms, sliced (Fungi)
• Unsalted butter (Fat)
• Granny Smith apples, cubed (Fruit)
• Granulated sugar (Sweetener)
• Grated Gruyere cheese (Dairy)
• Chives, minced (Herb)
• Dried thyme (Herb)
• Frozen puff pastry, thawed (Pastry)
• Egg, beaten (Binder)
• Salt and pepper

(Note: the full ingredients list, including measurements, is provided in the recipe card below.)

Variations

I love these Caramelized Onion, Mushroom, Apple & Gruyere Bites as is, but here are a few ideas for variations:

• Different Cheese: Use a different type of cheese, such as sharp cheddar, Swiss, or fontina.
• Add Bacon or Prosciutto: Add some cooked and crumbled bacon or diced prosciutto for extra savory flavor.
• Different Fruit: Use pears or figs instead of apples.
• Make it Spicy: Add a pinch of red pepper flakes to the filling.
• Add Nuts: Sprinkle some chopped walnuts or pecans on top of the filling before baking.

How to Make Caramelized Onion, Mushroom, Apple & Gruyere Bites

Let me show you how to make these elegant and flavorful Caramelized Onion, Mushroom, Apple & Gruyere Bites:

Preheat Oven and Prepare Baking Sheets

1. I preheat my oven to 400°F (204°C).
2. I line baking sheets with silicone baking mats or parchment paper. I set them aside.

Caramelize Onions

1. In a large skillet, I heat the vegetable oil.
2. I cook onions (with salt) until they’re golden brown, about 30 minutes.

Sautee Mushroom

1. Remove onions and set aside in a large bowl.
2. In the same skillet, I sauté the mushrooms until tender, about 5 minutes.
3. I remove and set aside in the bowl with onions

Cook Apples

1. In the same skillet, I melt the butter.
2. I add in the apples with the sugar.
3. I cook until softened, about 10 minutes.
4. I remove from pan

Combine Filling Ingredients

1. I add the cooked apples to the large bowl with the onions and mushrooms.
2. I add the Gruyere cheese, chives, and thyme to the bowl.
3. I stir to combine the mixture well.
4. I season with salt and pepper, to taste.

Prepare Puff Pastry

1. With a pizza cutter, I cut the thawed puff pastry into 2-inch squares.
2. I place them on the lined baking sheets.
3. Using a pastry brush, I brush the beaten egg on the squares.

Add Filling and Bake

1. Using a tablespoon, I place filling in the middle of each puff pastry square.
2. I bake for 25 minutes, rotating the pans halfway through and switching the baking sheet on the top rack to the bottom and the bottom to the top, until the pastry is golden brown and crisp.

Cool and Serve

1. I let the tarts cool a bit before serving.

Tips and Tricks for the BEST Bites

Here are my secrets for making these bites truly exceptional:

• Thaw Puff Pastry Properly: Thaw the puff pastry in the refrigerator overnight or according to package directions.
• Don’t Overfill: Don’t overfill the puff pastry squares, or the filling will spill out during baking.
• Bake Until Golden Brown: Bake the bites until the pastry is golden brown and crisp, and the cheese is melted and bubbly.
• Serve Warm: These bites are best served warm, when the cheese is melted and the pastry is flaky.

How to Serve

These Caramelized Onion, Mushroom, Apple & Gruyere Bites are perfect for:

• Appetizers: A delicious and elegant appetizer for holiday gatherings, parties, or any special occasion.
• Brunch: A savory and flavorful addition to your brunch menu.
• Snacks: A satisfying and sophisticated snack.

Make Ahead and Storage

You can prepare the filling ahead of time and store it in the refrigerator. You can also assemble the bites ahead of time and store them, unbaked, in the refrigerator for up to 24 hours. Bake just before serving. Leftover baked bites can be stored in an airtight container at room temperature for up to 2 days or in the refrigerator for up to 3 days. Reheat gently in the oven or toaster oven to re-crisp the pastry.

FAQs about Caramelized Onion, Mushroom, Apple & Gruyere Bites

• Can I use a different type of cheese?
  • Yes, you can use any type of cheese you like.
• Can I make these without the mushrooms or apples?
  • Yes, you can omit either the mushrooms or the apples, or both.
• Can I freeze these bites?
  • Yes, you can

Enjoy these elegant, flavorful, and easy-to-make Caramelized Onion, Mushroom, Apple & Gruyere Bites! They’re a perfect appetizer for any occasion.

Caramelized Onion, Mushroom, Apple & Gruyere Bites

• Author: Caoimhe Byrne
• Prep Time: 30 minutes
• Cook Time: 25 minutes
• Total Time: 55 minutes
• Yield: 48–64 bites 1x
• Category: Appetizer
• Cuisine: French-Inspired

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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.

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Ingredients

Scale 1x2x3x

• 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

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Instructions

• 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.

• 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.

• 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.

• 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.

• 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.

• Prepare Puff Pastry: Unfold the thawed puff pastry sheets on a lightly floured surface.

• Cut Puff Pastry: Using a pizza cutter or a sharp knife, cut each puff pastry sheet into 2-inch squares.

• Arrange on Baking Sheets: Place the puff pastry squares on the prepared baking sheets, leaving a little space between each square.

• Egg Wash: Brush the tops of the puff pastry squares with the beaten egg.

• Add Filling: Place a spoonful (about 1-2 teaspoons) of the filling in the center of each puff pastry square. Do not overfill.

• 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.

• Cool and Serve: Let the tarts cool slightly on the baking sheets before serving. Serve warm.

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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.