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Caramelized Onion Mushroom Apple Gruyere Bites

Caramelized onion mushroom apple Gruyere bites in crisp mini phyllo shells with jammy onions and browned mushrooms, finished with melted Gruyere. French-inspired appetizer with sweet apple and balsamic for a rich, savory 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: 210
Ingredients Equipment Method Notes

Ingredients
  

Butter
  • 2 tbsp butter
Onion
  • 1 large yellow onion thinly sliced
Mushrooms
  • 8 oz cremini mushrooms finely chopped
Apple
  • 1 small apple finely diced
Thyme
  • 1 tsp fresh thyme leaves
Balsamic vinegar
  • 1 tbsp balsamic vinegar
Salt and pepper
  • 1 salt and pepper to taste
Mini phyllo shells
  • 1 box (15 count) mini phyllo shells 24 used (2 boxes total)
Gruyere cheese
  • 1 cup shredded Gruyere
Fresh thyme for garnish
  • 1 fresh thyme for garnish

Equipment

  • 1 sheet pan

Method
 

Caramelize the base
  1. Melt the butter over medium-low heat, then add the thinly sliced onion and cook, stirring often, for 20-25 minutes until deep golden and jammy (steam should reduce and the onions should look glossy).
  2. Add the finely chopped cremini mushrooms and diced apple, then cook for 6-8 minutes until the mushrooms are browned and any liquid has evaporated (the mixture should look drier and more concentrated).
  3. Stir in the fresh thyme leaves and balsamic vinegar, then season with salt and pepper to taste (the mixture should smell fragrant and look evenly coated).
Bake the bites
  1. Preheat the oven to 350F and arrange the mini phyllo shells on a baking sheet (shells should be spaced so they bake crisp).
  2. Spoon the onion mixture into each shell, then top with shredded Gruyere (aim for an even mound in each cup).
  3. Bake for 8-10 minutes until the cheese is melted and the shells are crisp (you should see bubbling cheese at the edges).
  4. Garnish with fresh thyme for garnish and serve warm (top should look green and fresh right before serving).

Notes

For the jammi filling texture, cook the onions until they’re truly deep golden before adding mushrooms and apple—this keeps the filling from getting watery. Store assembled bites covered in the refrigerator up to 2 days, then re-crisp in a 350F oven for about 6-8 minutes. Freezing is not recommended for phyllo shells. Dietary swap: use a lactose-free shredded cheese blend to keep a similar melt and flavor.