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Caramelized Onion Mushroom Apple Gruyère Bites

Caramelized onion mushroom apple Gruyère bites bake in puff pastry cups until golden and flaky, with a savory-sweet filling and melted cheese. They’re assembled in a mini muffin pan and served warm as an easy party appetizer.
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Prep Time 35 minutes
Cook Time 49 minutes
Cooling and resting 15 minutes
Total Time 1 hour 39 minutes
Servings: 24 servings
Course: Appetizer
Cuisine: American
Calories: 145
Ingredients Equipment Method Notes

Ingredients
  

For the pastry cups
  • 1 package (17.3 oz) frozen puff pastry 2 sheets, thawed
For the filling
  • 1 tbsp olive oil
  • 1 tbsp unsalted butter
  • 0.5 yellow onion medium, thinly sliced
  • 0.25 tsp kosher salt
  • 0.125 tsp black pepper
  • 4 oz cremini mushrooms finely chopped
  • 0.5 apple medium, cored and finely diced
  • 1 tsp fresh thyme leaves
  • 1 tsp balsamic vinegar
For the topping
  • 4 oz Gruyère cheese finely shredded

Equipment

  • 1 10-inch skillet
  • 1 24-cup mini muffin pan

Method
 

Prepare the pastry
  1. Thaw the puff pastry according to package directions until pliable but still cold, about 30 to 40 minutes at room temperature.
  2. Heat the oven to 400°F.
Make the filling
  1. Heat the olive oil and butter in a 10-inch skillet over medium-low heat.
  2. Add the onion, salt, and pepper and cook, stirring often, for 18 to 22 minutes until deeply golden.
  3. Add the mushrooms and cook over medium heat, stirring often, for 6 to 8 minutes until browned and the skillet is dry.
  4. Stir in the apple and thyme and cook for 3 to 4 minutes until the apple is just tender.
  5. Stir in the balsamic vinegar and cook for 30 seconds.
  6. Transfer the filling to a bowl and cool for 10 minutes.
Assemble the bites
  1. Lightly grease a 24-cup mini muffin pan.
  2. Cut each puff pastry sheet into 12 pieces using a 3-by-4 grid.
  3. Press one piece into each cup with the corners extending above the rim.
  4. Spoon 1 tablespoon of filling into each pastry cup.
  5. Top each pastry cup with 2 teaspoons of Gruyère.
Bake the bites
  1. Bake for 15 to 18 minutes until the pastry is puffed and golden and the cheese is melted.
  2. Rest the bites in the pan for 5 minutes.
  3. Loosen them gently and serve warm.

Notes

Keep the puff pastry cold but pliable when assembling for the flakiest cups. Store leftovers in the refrigerator for up to 3 days; freeze baked bites for up to 2 months. For a dairy-free option, use dairy-free butter and cheese.