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Caramelized Onion Mushroom Apple Gruyere Bites

Caramelized onion mushroom apple Gruyere bites in crisp mini phyllo shells, topped with bubbling melted Gruyere. Sweet-savory jammy onions and browned mushrooms come together, then bake until the cheese melts and the shells turn crisp.
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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
Ingredients Equipment Method Notes

Ingredients
  

Onion and filling
  • 2 tbsp butter
  • 1 yellow onion
  • 8 oz cremini mushrooms
  • 1 apple
  • 1 tsp thyme leaves
  • 1 tbsp balsamic vinegar
  • 0.25 salt to taste
  • 0.25 pepper to taste
Phyllo cups and cheese
  • 24 mini phyllo shells use 24
  • 1 cup shredded Gruyere
  • 0.5 fresh thyme for garnish

Equipment

  • 1 sheet pan

Method
 

Caramelize the onions
  1. Melt the butter over medium-low heat, then add the thinly sliced yellow onion and cook 20-25 minutes, stirring often, until deep golden and jammy.
  2. Add the finely chopped cremini mushrooms and diced apple, then cook 6-8 minutes until the mushrooms are browned and the liquid evaporates.
  3. Stir in the thyme leaves and balsamic vinegar, then season with salt and pepper to taste.
Assemble and bake
  1. Preheat the oven to 350F, then arrange the mini phyllo shells on a baking sheet.
  2. Fill each 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.
  4. Garnish with fresh thyme and serve warm.

Notes

Pro tip: For extra crisp phyllo, keep the filling warm but not wet—if the pan looks glossy, cook 1-2 minutes longer to evaporate moisture. Store leftovers in the fridge up to 3 days; reheat at 350F until warmed. Freezing isn’t recommended because phyllo can soften after thawing. For a lighter option, use reduced-fat Gruyere (texture stays similar) while keeping the baking time the same.