1. Place the disc of dough on an oven tray.
2. Cover only half the dough with the crumbled sausages, fontina and mushrooms.
3. Boil the potatoes and mash.
4. Add the mashed potatoes to the topping to compact the filling.
5. Close the calzone over, taking care to seal the edges.
6. Bake at 230° for 7/8 minutes.