Squash-Blossom Pizzas

For the Dough: Sprinkle yeast over warm water in a large bowl; let stand until foamy, about 5 minutes. Stir in 3 cups flour and salt until smooth. Stir in remaining 2 cups flour (dough will be sticky).

Turn out dough onto a lightly floured work surface. With lightly floured hands, slap dough onto surface, pulling it toward you with one hand and pushing it away from you with the other. Fold dough back over itself. (Use a bench scraper or a wide spatula to help scrape dough from surface.) Repeat until dough is easier to handle, about 10 times. Finish kneading normally until dough is smooth, elastic, and soft but still a little tacky, about 10 minutes.

Shape dough into a ball and transfer to a lightly oiled bowl, turning to coat. Loosely cover with plastic wrap and let rise in a warm spot until doubled in bulk, 3 hours. (Press with your finger to see if it's done; an indent should remain.) Use dough immediately, refrigerate overnight, or freeze in an oiled resealable plastic bag up to 3 months.

For the Pizzas: Line a baking sheet with parchment; lightly dust with flour. On a lightly floured surface, cut dough into 4 pieces and form into balls. Dust with flour; loosely cover with plastic wrap. Let rest until dough is relaxed and almost doubled in size, 20 to 30 minutes.

Working with one dough ball at a time and keeping remaining balls covered, hold top edge in both hands, letting bottom edge touch work surface. Carefully move hands around edge to form a circle, as if turning a wheel. Hold dough on back of your hand, letting its weight stretch it into a rough 10-inch round. Transfer to baking sheet. Using your fingers, press out edges.

Preheat oven to 500 degrees, with a pizza stone or an inverted baking sheet on lowest rack. Brush dough with oil; spread with 4 ounces ricotta. Top with 4 ounces mozzarella and sprinkle with 1 tablespoon Parmesan. Toss one-quarter of zucchini slices and one-quarter of halved blossoms with 1 tablespoon oil in a bowl; season with salt and pepper. Arrange zucchini mixture on top of cheese.

Slide pizza and parchment off baking sheet onto pizza stone. Bake until crust is crisp and cheese is golden brown, 18 to 20 minutes. If you like, crack an egg into a teacup and gently pour it on top in the last 5 minutes of baking. Remove pizza from oven by sliding parchment onto baking sheet. Top with 1 tablespoon herbs. Serve immediately, with red-pepper flakes. Repeat with remaining dough and toppings.