Add a half slice of prosciutto in the middle of the triangle and top with parmesan cheese. Bring the two longer corners together, pinch to secure, and place on the prepared sheet pan.
To Bake:
Place the sheet pan in the preheated 400-degree oven and bake for 8 minutes, then turn the pan in the oven to help with even browning. Bake for another 8-10 minutes or until pastry is puffed and nicely browned.
**Note if making in advance and freezing. Cook until just lightly browned, usually just the first 8 minutes. Remove, cool and place in airtight containers and freeze. To heat, add the frozen pieces to a sheet pan, place in the preheated 400-degree oven and bake for about 10 minutes or until golden brown.
Each piece will be 2-3 bites. After the pieces are baked, they can be cut in half if desired.