Rich, milky fresh mozzarella is the ideal complement for garlicky mortadella on this pizza. A sprinkling of red-pepper flakes before serving adds a welcome dose of heat.
Place a pizza stone on floor of gas oven (remove racks) or bottom rack of electric oven. Preheat oven to at least 500 degrees for 1 hour.
Meanwhile, arrange cheese evenly over dough, leaving a 1-inch border. Top with mortadella, garlic, and thyme. Drizzle with oil.
Switch oven to broiler setting. Align edge of peel with edge of stone. Tilt peel, jerking it gently to move pizza. When edge of pizza touches stone, quickly pull back peel to transfer pizza to stone. (Do not move pizza.) Broil until bubbles begin to form in crust, 3 to 4 minutes. Reduce temperature to 500 degrees; bake until crust is crisp and golden brown, 6 to 8 minutes more. (If not using broiler, bake pizza 10 to 15 minutes total.) Remove pizza from oven using peel. Drizzle with more oil and sprinkle with red-pepper flakes. Slice and serve.
Mozzarella di bufala is available at most supermarkets. Mortadella, a smoked sausage, is available at specialty-food stores.