Preheat oven to 500 degrees. Place the pizza stone in oven to preheat. Alternatively, lightly brush a sheet pan with oil. Set aside. Add the oil and garlic to a small saucepan and heat over low heat to infuse the oil with the garlic.
Meanwhile, shape pizza dough into an 8 or 9-inch circle. If using a pizza stone, shape the dough on a board. If using a sheet pan, shape the dough directly on the pan.
Brush the dough with the garlic-infused oil. Top with the parmesan cheese. Layer some of the gruyere, the prosciutto, leeks and finish with the remaining gruyere. Season with freshly ground black pepper.
Transfer to the hot pizza stone or place sheet pan in the oven. Bake for 15-20 minutes or until crust is golden brown, prosciutto is slightly crisp, and cheese is melted. Sprinkle with additional parmesan cheese. Slice and serve.