saute sausage (meat out of casing) until cooked, set aside. Add onions to pot and add a little olive oil if needed, saute until caramelized. add in garlic, salt pepper and mushrooms. Cook until soft add in sausage and mix well.
Roll out puff pastry to form 2 rectangles and put filling in center, add mozzarella and wrap.
Bake according to puff pastry dough until browned.