Step 1

Combine water, sugar, and yeast. Stir to dissolve and let stand 5 minutes. Add all-purpose flour and beat 1 minute. Cover and let stand at room temperature 8 hours.

Step 2

Add to the sponge milk, oil, salt, and enough bread flour to make a soft dough. Turn out onto a floured work surface and knead 8 to 10 minutes. Add flour only to reduce stickiness. Return to bowl, dust with flour, cover with plastic, and rise at room temperature until doubled in volume, about 1 hour.

Step 3

Line a baking sheet with parchment and dust with cornmeal. Turn dough onto a floured surface and divide into 2 equal portions. Roll each piece into a football shape, no longer than the width of the baking sheet. Taper the ends slightly. Place loaves on the pan, dust with flour, cover with plastic wrap, and rise another 30 minutes. Preheat oven to 400°F.

Step 4

Using a serrated knife, score 1⁄4-inch-deep angled cuts into the top of each loaf. Place a pan of cold water at the bottom of the oven to create steam. Bake until golden brown and firm, about 20 to 30 minutes. Remove to a rack and cool completely before slicing.