Preheat your oven at 400 F.
In a frying pan, sautée 1 tsp of garlic in olive oil add the mushrooms, salt and pepper. When they soften, add the tbsp of truffle oil. Set aside.
In a food processor, blend the goat cheese with Greek yogurt. Add the finely chopped parsley.
Roll the sheet of puff pastry (store bought block for a shortcut). With a knife, trace a border of approximately 2cm and spread inside the border with the goat cheese mixture.
Place the mushrooms on top and add the Parmesan cheese. With a small basting brush, paint the border of the puff pastry with some of the beaten egg and salt. Bake for 25 minutes.