Preheat oven to 450

For the béchamel sauce base, pour the milk into a small saucepan and bring to a simmer over medium heat, Melt the butter in a medium saucepan over medium-low heat. Whisk the flour into the butter and cook for 2 minutes, whisking constantly. Whisk in the hot milk, switch to a wooden spoon and simmer, stirring constantly, for 2 to 5 minutes, until thick enough to leave a trail when you run your finger down the back of a spoon. Cook for one more minute. Off the heat, stir in the ricotta, egg yolks, salt and pepper to taste; set aside.

Heat 1 tablespoon olive oil in a medium pan, add the pancetta and cook over medium heat for 4 minutes, stirring occasionally, until half-cooked. Transfer the pancetta to a plate lined with paper towels and set aside.

Flip over a sheet pan and cover with a piece of parchment paper (or with silicone baking sheet). Split the dough in half and then roll and stretch the pizza dough into 2- 9- or 10-inch circle on the parchment paper. Leaving a 1-inch border, spread 1/2 cup of the béchamel on each pizza and sprinkle with 2 tablespoons of the Parmesan, 2 tablespoons of the Pecorino and half of the pancetta. In a medium bowl, toss the Brussels sprouts with about 3 tablespoons olive oil. Sprinkle the two pizzas evenly with the Brussels sprouts. Bake for 15 to 20 minutes, until the crust is nicely browned, including the bottom. Cut each pizza into wedges and serve hot.