Place balsamic vinegar in a small skillet or saucepan and cook over medium heat, stirring frequently, until it bubbles and reduces to a thick, syrup-y consistency, about 7-10 minutes. Remove from heat and set aside. The balsamic reduction will continue to thicken a bit as it cools.

Heat oven to 500° F with a baking steel or pizza stone inside. For best results, let the oven heat for 30-60 minutes to get the baking steel nice and hot.

Lay a piece of parchment paper over a large cutting board. Roll or stretch the pizza dough into shape and place on top of the parchment paper (this will make it easier to slide into the oven!).

Top the pizza dough with a drizzle of olive oil, followed by the torn mozzarella cheese, then the prosciutto, and a pinch of salt and pepper.

Slide pizza into the hot oven and bake until pizza is browned and the cheese is bubbling, about 10-15 minutes. The exact time will vary depending on your oven, equipment, and pizza dough: check it every few minutes and pull it out of the oven as soon as it looks done!

Use a pair of tongs to carefully pull the finished pizza out of the oven and onto your cutting board. Transfer pizza to a wire cooling rack for 5-10 minutes (a cooling rack helps the crust stay crispy) then return to the cutting board.

Top pizza with fresh arugula and a drizzle of your balsamic reduction. Slice and serve immediately.