Preheat oven to 425 degrees then line a baking sheet with parchment paper. Thaw the pastry according to the packaging directions, roll out the pastry slightly on a lightly floured surface. Transfer to the lined baking sheet.
Spread pizza sauce over the pastry, leaving a ½ inch border. Tear the prosciutto into bite size pieces and lay over the pastry, place sliced mushrooms, and onions between prosciutto pieces. Tear fresh mozzarella into small pieces and sprinkle pizza generously with the mozzarella and fresh grated Grana Padano cheese.
Bake 15-20 minutes until the cheese is melted, and the pastry crust is golden brown. I put more bite size pieces of prosciutto on top of the pizza after taking out of the oven while it was still hot ans sprinkled with sliced basil.
Once out of the oven,let cool for 2 minutes. Slice and serve! Enjoy!