1 tsp olive oil
1 yellow onion, thinly sliced
1 Tablespoon unsalted butter
8 oz. white button mushrooms, chopped
1 clove garlic, chopped
1/2 tsp dried thyme
Salt and pepper, to taste
1/4 cup white wine
1 sheet puff pastry, thawed
1/2 cup shredded Gruyere cheese, or any variety of Swiss cheese
Egg wash (one egg and one Tablespoon water, beaten together)
Heat olive oil over medium-low heat, and add the onions. Cook, stirring occaisionally, until they begin to caramelize, about 20 minutes.
Stir in butter and add mushrooms. Cook until soft and liquid has evaporated, about 20 minutes.
Add garlic and thyme. Cook until fragrant, about one minute.
Stir in white wine, scraping the bottom of the pan to pull up all of the browned bits. Cook until all of the liquid has evaporated.
Unfold thawed puff pastry sheet, and cut into squares. Place on parchment paper lined baking sheet.
Using a sharp knife, make four small scores around the perimeter of the dough, about 1/4-1/2 inch from the edge.
Top with a small spoonful of the onion and mushroom mixture, keeping it inside of the score marks. Top with cheese.
Brush edges of dough with egg wash.
Bake at 400* for 15-25 minutes.