Place a baking stone on the lower rack of the oven and preheat to 475 degrees F.
Remove the dough from the bowl and briefly knead. Place on a lightly floured work surface and let rest for 10 minutes. Shape into a 16-inch round. Lightly dust a baker's peel with the cornmeal. Transfer the dough to the peel. (Alternately, the dough can rest and then be cooked on a lightly oiled baking sheet.)
Working 1 1/2 inches in from the outer edge, sprinkle 1 cup of the cheese in an even border around the crust. Fold the outer 1-inch of crust over the cheese and press to seal.
Over a small bowl, squeeze each head of garlic gently with your fingers to expel the cloves. Add the olive oil and stir with a rubber spatula to blend thoroughly. Spread the mixture over the pizza crust. Using a small scoop or tablespoon, spoon dollops of ricotta over the crust. Spread the spinach evenly over the crust and top with the remaining 1 1/4 cups mozzarella cheese. Transfer to the baking stone and cook until the crust is golden brown and the cheese is melted, 8 to 10 minutes. Remove from oven and let rest for 5 minutes before slicing. Serve hot.
Yield: 1 (14-inch) pizza