Ingredients:
1 sheet puff pastry, thawed
2 large onions, thinly sliced
8 oz mushrooms, sliced (cremini or button)
2 tablespoons olive oil
1 tablespoon butter
2 cloves garlic, minced
1 teaspoon thyme (fresh or dried)
1 cup Gruyère cheese, grated
1/2 cup sour cream
Salt and pepper to taste
Fresh parsley for garnish
To the instructions