Preparation

• Put a pizza stone on the lowest rack of the oven, heat the oven to 550°F, and let the stone heat for at least a half-hour.
• Cut half of the mozzarella into 1/2-inch dice and put in a medium bowl. Thinly slice the other half and, using the side of a chef’s knife, mash it into a paste. Add it to the diced mozzarella. Add the Parmigiano, cream, and buttermilk, and season lightly with salt.
• Lightly flour a pizza peel. Stretch one dough ball into a 10- to 11-inch round and transfer it to the peel. Spread half of the cheese mixture over the dough almost to the edge and season with black pepper. Slide the dough onto the hot stone and bake until the cheese is melted and the crust is nicely browned, about 8 minutes. Transfer to a cutting board and slice. Drape half the prosciutto over the pizza. Toss the arugula with just enough olive oil to dress it very lightly. Season with salt and pepper and scatter half over the prosciutto. Repeat to make the second pizza.