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1
Stir together water, yeast, and sugar in a large bowl and let stand until foamy, about 10 minutes.
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2
(If mixture doesnt foam, discard and start over.)
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3
Stir in oil, flour, cornmeal, and table salt, then stir until a dough forms.
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4
Knead on a floured surface, dusting with more flour as needed to prevent dough from sticking, until smooth and elastic, 5 to 10 minutes (dough will be moist).
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5
Put dough in an oiled deep bowl and turn to coat with oil.
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6
Let dough rise, covered with plastic wrap, in a warm place until doubled in bulk, about 1 hour.
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7
Punch down dough and divide into 6 balls.
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8
Roll out 1 ball of dough 1/8 inch thick (about 7 inches in diameter) on a lightly floured surface.
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9
Brush off excess flour, then transfer dough to a lightly oiled baking sheet and cover surface of dough completely with plastic wrap.
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10
Roll out remaining balls of dough in same manner, covering with plastic wrap and stacking rounds.
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11
Wrap baking sheet with more plastic wrap.
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12
Chill dough until firm, about 2 to 4 hours or overnight.
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13
Preheat oven to 425F.
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14
Thinly slice potatoes (1/8 inch thick) using a mandoline or other manual slicer, then toss with oil, garlic, salt, rosemary, and pepper in a large bowl until lightly coated.
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15
Spread potatoes in 1 layer on 2 lightly oiled baking sheets.
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16
Bake in upper and lower thirds of oven, switching position of sheets halfway through baking, until tender, about 15 minutes total.
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17
Cool potatoes on sheets on racks.
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18
Prepare grill for cooking.
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19
Remove plastic from 3 dough rounds (if grill is not large, work with 1 piece at a time) and lightly brush dough with some oil.
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20
When the fire is medium-hot (you can hold your hand 5 inches above rack 3 to 4 seconds), carefully transfer dough, trying not to stretch it, oiled side down, with your hands to grill rack.
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21
Grill oiled rounds until undersides are browned, 3 to 4 minutes.
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22
Flip over with tongs, then, working quickly, sprinkle each crust with 1/3 cup mozzarella and cover with potato slices, overlapping them and leaving a 1/4-inch border around edge.
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23
Grill, covered, until undersides are golden and cheese is melted, about 4 minutes.
