Preheat your oven to 400°F (200°C) and grease six 6-ounce ramekins with butter or cooking spray.

Roll out thawed puff pastry to about 1/8-inch thickness and cut out circles to cover each ramekin.

Melt butter in a skillet over medium heat and sauté chopped onion for about 4 minutes until translucent.

Add minced garlic and cook for another minute, then stir in mixed mushrooms and cook for 8-10 minutes.

Sprinkle in flour and thyme, stirring to combine and cook for about 2 minutes until roux forms.

Gradually pour in vegetable broth while stirring, then mix in heavy cream and bring to a simmer for about 5 minutes.

Season filling with salt and black pepper, then divide among prepared ramekins.

Sprinkle shredded Gruyère cheese on top of each filling.

Cover with puff pastry circles, pressing edges to seal.

Brush tops with beaten egg and make small slits to allow steam to escape.

Bake for 15-20 minutes until the pastry is puffed and golden brown.

Let the pot pies cool for a few minutes before serving.