ZUCCHINI, POTATO, AND FONTINA PIZZETTAS

Steps:

• Whisk yeast, sugar, and 3 Tbsp. warm water in a large bowl. Let sit until surface is foamy, about 5 minutes. Add 1 1/4 cups room-temperature water, then add 1 cup flour, whisking until smooth (mixture should be the consistency of pancake batter). Add 2 1/2 cups flour and 2 tsp. kosher salt and mix with a wooden spoon until a shaggy dough forms.
• Turn out dough onto a lightly floured surface and knead with your hands, adding more flour as needed to prevent it from sticking, until dough is smooth and supple, 5-10 minutes (it will be very soft). Transfer to a large oiled bowl and cover with plastic wrap. Let rise in a warm, draft-free spot until doubled in size, 1-1 1/2 hours.
• Divide dough into 4 equal pieces and form into balls. Place on an oiled rimmed baking sheet and cover with plastic wrap; let rise in a warm, draft-free spot until balls of dough are nearly doubled in size, 40-50 minutes.
• Meanwhile, place potato slices in a colander and rinse with cold water. Drain, season with kosher salt, and let sit, tossing occasionally, until softened, 10-15 minutes. Transfer to a bowl and toss with onion, zucchini, and 2 Tbsp. oil; set aside.
• Preheat oven to 450°F. Working with 1 ball of dough at a time and keeping remaining dough covered while you work, roll out dough on a lightly floured surface into 10" rounds.
• Heat a dry large cast-iron skillet over medium. Pour 1 Tbsp. oil into skillet and cook a dough round until bottom is golden brown and top looks dry, about 1 minute. Flip and cook just until bottom is lightly golden, about 1 minute. Transfer to a rimmed baking sheet and repeat with remaining 3 Tbsp. oil and rounds of dough (you should be able to fit two pizzettas per baking sheet if you overlap them slightly).
• Top pizzettas with Fontina cheese and reserved potato mixture; season with kosher salt. Bake, rotating baking sheets once top to bottom and back to front, until crusts are golden brown and crisp and cheese is bubbling, 10-15 minutes. Remove pizzettas from oven, season with sea salt and pepper, and drizzle with oil.