Jewish Sour Rye

Sponge
3/4 cup (4 ounces, 117 grams) bread flour
3/4 cup (3.3 ounces, 95 grams) rye flour
1/2 teaspoon (1.6 grams) instant yeast
1 1/2 tablespoons (0.6 ounces, 18.7 grams) sugar
1/2 tablespoon (10.5 grams) barley malt syrup
1 1/2 cups (12.5 ounces, 354 grams) water, at room temperature

Flour Mixture
2 1/4 cups (12.5 ounces, 351 grams) bread flour
1/2 plus 1/8 teaspoon (2 grams) instant yeast
2 tablespoons (0.5 ounces, 14 grams) caraway seeds
1/2 tablespoon (0.3 ounces, 10.5 grams) salt

Dough and Baking
1/2 tablespoon (0.25 ounces, 6.7 grams) vegetable oil
about 2 teaspoons (about 0.5 ounces, 16 grams) cornmeal for sprinkling

Make the sponge: Combine sponge ingredients in a large or mixer bowl and whisk until very smooth. Set it aside.

Make the flour mixture and cover the sponge: In a separate large bowl, whisk together the flour mixture and gently scoop it over the sponge to cover it completely. Cover the bowl tightly with plastic wrap and allow it to ferment for 1 to 4 hours at room temperature. (The sponge will bubble through the flour mixture in places.)

Mix the dough Add the oil and mix with the dough hook on low speed for about 1 minute, until the flour is moistened enough to form a rough dough. then raise the speed to medium and mix it for 10 minutes. The dough should be very smooth and elastic, and it should jump back when pressed with a fingertip; if it is sticky, turn it out on a counter and knead in a little extra flour.

Let the dough rise: Place the dough in a large container or bowl, lightly oiled. Oil the top of the dough as well. Allow the dough to rise until doubled, 1 1/2 to 2 hours. Let the dough fall out on to a lightly floured counter, press it down gently, fold or form it back into a square-ish ball and allow it to rise a second time, back in the bowl covered with plastic wrap for about 45 minutes.

Turn the dough out onto a lightly floured counter and gently press it down again. Round it into a ball and set it on a cornmeal sprinkled baking sheet, or on a cornmeal-covered piece of parchment paper on the bottom of La Cloche. Cover it with oiled plastic wrap and let it rise until almost doubled, about 1 hour to 1 hour 15 minutes.

Preheat the oven to 450°F an hour ahead of time. On a shelf at the lowest level, place a baking sheet or bread stone. Unless you're using La Cloche, place a cast-iron skillet or sheet pan on the floor of the oven (or the bottom shelf) to preheat.

Slash and bake the bread: With a sharp knife or singled-edged razor blade, make 1/4- to 1/2-inch-deep slashes in the top of the dough. Put it in oven; if you're using La Cloche, cover it with preheated top dome. Otherwise, toss1/2 cup of ice cubes into the pan beneath and immediately shut the door. Bake for 15 minutes, lower the temperature to 400°F and continue baking for 30 to 40 minutes or until the bread is golden brown and a skewer inserted into the middle comes out clean.

Cool the bread on a wire rack.