Position a pizza stone on a rack in the center of the oven, and heat to 450°F.
Bring a pot of salted water to a boil, and cook the potato slices for 1 minute. Rinse under cold water, gently pat dry with paper towels, and set aside.
In a 12-inch skillet, heat 2 Tbs. oil over medium-high heat. add the rosemary and cook, stirring often, until crisp, about 1 minute. Transfer to a paper-towel-lined plate. Add the broccoli rabe to the skillet and cook, stirring occasionally, until the stalks are crisp-tender, about 3 minutes.
Generously flour a pizza peel or a large cookie sheet. Stretch the pizza dough on the peel to a 14-inch circle. Evenly distribute half of both mozzarellas over the dough, then half of the potatoes, half of the broccoli rabe, and all of the garlic, covering most of the surface. Crumble the fried rosemary leaves over the pizza. Repeat with the remaining potatoes, broccoli rabe, and mozzarella. Season with a pinch of salt and a few generous grinds of pepper, and carefully slide onto the pizza stone.
Bake until the crust is browned and the cheese is just melted, 13 to 15 minutes. Remove the pizza from the oven, top with the grana Padano, and drizzle with the remaining oil. Cool briefly and serve.
nutrition information (per serving):
330, Fat Calories
15, Saturated Fat
6, Polyunsaturated Fat
0.5, Monounsaturated Fat
Photo: Scott Phillips