Preheat the oven on 400° F.
Combine the mushroom with white pepper, and shredded Italian Fontina. If you prefer, use another kind of cheese easy to melt into the oven. Cut the bread into big slices. When the oven has reached the right temperature, bake the bread slices until light crispy. Now, spread the mixture of cheese and mushrooms over the bread, and bake 10 minutes. Finally, broil 2-3 minutes until crispy and golden brown. Serve the mushrooms cheese crostini just out from the oven, very hot!