2. Heat the olive oil in a large skillet over medium-high heat. Add the onions and mushrooms and cook until they begin to soften. Season with salt and pepper. Turn the heat to high and lightly brown the onions and mushrooms. Add the garlic and cook for 1 minute more.
3. Place the Classic Pizza Dough or pizza shell (thawed if frozen) on a baking sheet and spread the onion mixture on top, leaving the edge of the pizza free.
4. Bake until nicely browned and crispy, about 15 minutes. Sprinkle with Parmesan cheese and cover the top with arugula leaves and slices of prosciutto. Drizzle with the remaining teaspoon of olive oil. Cut the pizza into 8 slices and serve.