Easy Pan Pizza with Potato, Onion, and Rosemary

Ingredients

• 1 recipe Foolproof Pan Pizza, or 1 1/2 pounds store-bought pizza dough
• 1 pound Yukon gold potatoes
• Kosher salt
• 1/2 cup extra virgin olive oil
• 1 small yellow onion, finely sliced
• 2 tablespoons roughly chopped fresh rosemary leaves
• Freshly ground black pepper

Directions

1. Split the dough into 2 equal pieces and shape them into balls. Add 2 tablespoons of oil to the bottom of each of two 10-inch cast iron skillets or round cake pans. Set 1 dough ball in each pan, then turn it so it is coated in oil. With a flat hand, gently press the dough outward to flatten it a bit and move the oil across the bottom and up the sides of the pan. Cover the pans snugly with plastic wrap and leave the dough at room temperature for two hours. After the first hour, move an oven rack to the lower middle position and heat the oven to 550 degrees F.
2. As the dough rises, prepare the mashed potatoes. Peel and roughly dice 1 potato, then place it in a medium saucepan and cover it with salted water. Cook until the potato is tender, about 15 minutes. Drain it, pass it through a ricer, and put it back into the empty pot. Stir in two tablespoons extra-virgin olive oil, season with salt and pepper, and fold everything together with a wooden spoon until combined. Set the mashed potatoes aside.
3. While that is happening, cut the remaining two potatoes into 1/8th inch thick slices, using a mandoline-style cutter if needed. Put the slices in a large bowl of water as you work. Once all the potatoes are sliced, drain and rinse them, then dry them carefully in a salad spinner or with paper towels. Put them back in the bowl, add the onions, remaining 2 tablespoons olive oil olive oil, and rosemary, then season with salt and pepper. Toss until coated and set aside.
4. When the dough has risen for two hours, it should nearly reach the sides of the pan. Use your fingertips to nudge it outward until it fills every corner, pressing out any big bubbles that show up. Lift one edge of the dough so trapped air underneath can slip out, then continue around the dough until no air pockets remain underneath and the dough is spread evenly in the pan.
5. Arrange the potato slices over the pizzas, allowing some onion to stay attached and overlapping the slices into a nice pattern. Scatter any leftover onion, rosemary, and oil over the tops. With a small spoon, dot the pizzas with the mashed potatoes in 1-inch dollops.
6. Bake until the potato edges are browned, the mashed potato dollops are crisp and browned, and the undersides of the pizzas are golden and crunchy, about 15 minutes. Take the pizzas out of the oven and serve right away.