Prep the toppings: Cut the top 1/4 off the head of garlic, exposing the cloves. Place it on top of a piece of aluminum foil and drizzle 1 tablespoon olive oil over it. Wrap it fully in the foil and roast at 400°F until the garlic is caramelized and golden, 25-30 minutes. Set aside to cool. Reduce oven temperature to 375°F.
In a large sauté pan, heat the remaining olive oil over medium heat. Add the broccoli rabe and sauté until just barely tender, 6-8 minutes. Season with pepper flakes, salt, and pepper. Set aside to cool.
Make the bechamel: In a medium pot, melt the butter over medium heat. Add the flour and stir to combine. Cook, stirring constantly, until the mixture turns lightly golden, 2-3 minutes.
Stir in the milk and bring to a simmer. Simmer until the sauce is thick, 3-5 minutes. Season with nutmeg, salt, and pepper.
Make the pizza: Generously oil a 12-inch oven-safe skillet with olive oil.
Using lightly floured or oiled hands, press the dough out into a large circle shape. Use your hands to gently stretch the dough at the edges until it is slightly larger than the pan.
Transfer the dough to the pan and turn it over to coat it on both sides with oil. Use your fingers to stipple it all over with your fingers to make it evenly cover the base of the pan—it should come up the sides of the pan, too, almost to the edge.
Let the dough rest for 15-20 minutes. Squeeze the cooled roasted garlic cloves out of their skin.
Add a thin layer of bechamel (about 1/3 cup) on top of the crust and spread into an even layer. Layer the roasted garlic and broccoli rabe on top of the sauce. Dollop the ricotta over the surface, then sprinkle the mozzarella over the whole thing.
Drizzle the remaining bechamel on top of the pizza. Bake the pizza until the edges are golden brown and the sauce is bubbly, 35-40 minutes.
Let cool at least 15 minutes before slicing and serving.
I always carry three kinds of hot sauce in my purse. I have a soft spot for making people their favorite dessert, especially if it's pie. My first cookbook, The Fearless Baker, is out on October 24, 2017.