1Place a pizza stone in the oven and preheat to 500°F for 1 hour before baking. (Or preheat a wood-fired pizza oven to very hot, 4 hours before baking.)
2Sprinkle one-fourth of the cheese on 1 disc of dough, leaving a 1-inch border all around.
3Gently place the pizza on the pizza stone and bake for about 5 minutes, until golden with slight signs of charring. (If using a wood-fired oven, gently place the pizza on the oven floor, and bake for 3 minutes, or until golden and crisp.)
4Remove the pizza from the oven, transfer to a cutting board, and top with one-fourth of the prosciutto and 1 handful of the arugula. Drizzle with olive oil and season with salt and pepper. Slice and serve immediately.
5Repeat with the remaining 3 pizza discs.