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Caramelized Onion Mushroom Apple Gruyere Bites

Caramelized Onion Mushroom Apple Gruyere Bites with jammy onions, browned mushrooms, and diced apple tucked into crisp mini phyllo shells, then baked until Gruyere melts. French-inspired flavor with balsamic, fresh thyme, and a bubbly, golden top in every bite.
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Prep Time 15 minutes
Cook Time 40 minutes
Total Time 55 minutes
Servings: 24 servings
Course: Appetizer, Snack
Cuisine: French-inspired
Calories: 165
Ingredients Equipment Method Notes

Ingredients
  

Butter
  • 2 tbsp butter Use for caramelizing the onions.
Onion, mushrooms, and apple
  • 1 large yellow onion Thinly sliced for jammy caramelized onions.
  • 8 oz cremini mushrooms Finely chopped for browning and moisture evaporation.
  • 1 small apple Finely diced for sweet, tender bites.
  • 1 tsp fresh thyme leaves Fresh herb for fragrance.
  • 1 tbsp balsamic vinegar Adds tang to balance sweetness.
  • 0.5 salt and pepper To taste; season at the end of cooking.
Phyllo and cheese
  • 24 mini phyllo shells (24 used) Use 24 mini shells (from two 15-count boxes).
  • 1 cup shredded Gruyere For melty, bubbly topping.
  • 0.5 fresh thyme for garnish Optional but recommended for finishing.

Equipment

  • 1 sheet pan

Method
 

Caramelize the onions
  1. Melt the butter in a pan over medium-low heat, then cook the thinly sliced onion for 20-25 minutes, stirring often, until deep golden and jammy.
  2. If the pan looks dry, lower the heat slightly and continue stirring so the onions caramelize evenly without burning.
Cook mushrooms and apple
  1. Add the finely chopped mushrooms and the finely diced apple, then cook for 6-8 minutes until the mushrooms are browned and the liquid evaporates.
  2. Keep stirring occasionally so the mushrooms brown instead of steaming.
Season the filling
  1. Stir in the fresh thyme leaves and balsamic vinegar, then season with salt and pepper to taste.
  2. Cook for 30-60 seconds after adding balsamic so the flavor disperses throughout the mixture.
Fill and bake
  1. Preheat the oven to 350°F, then arrange the mini phyllo shells on a sheet pan.
  2. Fill each phyllo shell with the onion mixture, then top with shredded Gruyere.
  3. Bake for 8-10 minutes until the cheese is melted and the shells are crisp.
Serve
  1. Garnish with fresh thyme and serve warm.

Notes

For the jammiest filling, cook the onions low and stir often until they turn deep golden, then fully evaporate the mushroom liquid so the phyllo stays crisp. Store leftovers in the refrigerator up to 3 days; reheat at 325°F for 5-7 minutes to re-crisp. Freezing isn’t recommended because phyllo tends to soften. For a dairy swap, use a melting cheese blend instead of Gruyere to keep the bake-and-brown result.