Put a large, heavy baking sheet (17x14) on lowest rack of oven and preheat oven to 500F.

Roll out dough on a lightly floured surface with a floured rolling pin, stretching corners with your hands to form a 16x13 rectangle (dough will be easier to roll as it warms). Transfer to a large tray lined with a sheet of parchment paper. Lightly dock the dough with a fork and then brush with olive oil. Slide dough (on parchment) onto hot baking sheet. Bake until top is puffed and pale golden in patches, 6-10 minutes. Prick any large bubbles with a fork and flatten.

While crust bakes, shred cheese in a food processor fitted with medium shredding disk (should yield about 3 cups).

Remove crust from oven and brush all over with crushed garlic, then sprinkle evenly with cheese. Return pizza to oven and bake until edge of crust is deep golden brown and cheese is bubbling and gloden in patches - approx another 8-10 minutes.

Remove from oven, scatter arugula over pizza and drape prosciutto over arugula. Drizzel with oil and coarsely ground pepper, to taste. Slice and serve immediately.