Step 1

In a large bowl, combine the rye flour, water, and yeast, stirring until the mixture is completely smooth.

Step 2

Tie the onion and caraway seeds together tightly in cheesecloth fashioned like a homemade tea bag and then sink the bag completely into the flour mixture.

Step 3

Cover the bowl tightly with plastic wrap and place it in a nice warm spot (70° to 75°F|21° to 24°C) and leave it overnight until it’s thick and airy, sorta like whipped cream. Remove the bag, scraping the sour mixture off the bag and back into the bowl, and discard the cheesecloth bag.

Step 4

Add the water and rye flour to the sour and mix until smooth. Cover with plastic and let it ferment at room temperature until it’s visibly fermented and frothy and quite possibly almost double in size, 3 to 4 hours more.

Step 5

The rye sour can now be used to make your rye bread recipe. You’ll probably have plenty leftover to put in the fridge. The sour may be kept alive and well in the refrigerator forever if it is fed regularly. Store it in a tightly sealed container and feed it once a week. The chopped onion and whole caraway seeds should have been removed by now and discarded after the first day and not used in future feedings. (See instructions below.)

Step 6

Turn the sour into a large bowl, add the water and rye flour, and mix until smooth. Cover with plastic wrap and let ferment at room temperature until it’s nice and frothy and full of fermentation bubbles, 3 to 4 hours. The rye sour can now be used to make your rye bread recipe. Or you can put it back in a tightly sealed container and return it to the refrigerator where it will be okay for another week. Feed the sour at least once per week and you will be able to use it indefinitely.

Step 7

Take the bread, break it into pieces, and moisten it with 1⁄4 cup plus 3 tablespoons water. Let sit for 15 minutes. Measure out 1⁄4 cup (95 g) of the bread and water mixture.

Step 8

In a large, wide bowl combine the rye sour starter, the remaining 3/4 cup water, the wet bread mixture, instant yeast, and ground caraway. Stir with a wooden spoon until well blended. Add 1 3/4 cups of the flour and stir until the mixture looks like thick pancake batter, about 2 minutes. Add the salt and remaining flour and stir until it starts to form a gloriously shaggy mess.

Step 9

Scrape the dough out of the bowl and onto a clean, unfloured work surface and gently knead until it forms a smooth ball, 6 to 8 minutes. If the dough begins to stick to the surface, use a plastic scraper to scrape it up and maybe even to scrape the dough from your hands. (Rye has a different chemical makeup than wheat flour and tends to be sticky. Don’t be alarmed if that’s the case and resist the temptation to add flour. Keep gently kneading and the dough will come together.)

Step 10

Lightly oil the bowl, place the dough back in the bowl, and cover with plastic wrap. Let it ferment at room temperature until the dough has increased in size by about 50%, roughly 60 to 90 minutes.

Step 11

Uncover the dough and turn it out onto a lightly floured work surface. Divide the dough into 2 equal pieces. Gently shape both pieces into rounds and cover with plastic. Let rest for 30 minutes.

Step 12

Shape the rounds into loaf shapes. Place on a cornmeal-coated cutting board and cover with plastic wrap.

Step 13

Preheat the oven to 450°F (230°C) and adjust the oven rack to the middle position. Place a baking stone on the rack and a cast iron skillet on the lowest rack or bottom of the oven about 1/2 inch (12 mm) away from the door so it’s accessible to add ice (to create steam to hydrate the bread while it bakes). Preheat the oven for 45 minutes before baking. Have ready a large stainless steel bowl or aluminum roasting pan that’s larger than your baking stone.

Step 14

While the oven is preheating, let the loaves rest and continue to ferment for 30 to 60 minutes. When you think it’s ready, gently touch the dough with a finger to see if it is ready for the oven. If the indentation is slow to fill back in, the loaf is ready for baking. If it fills back in quickly, give it about 15 more minutes.

Step 15

Uncover the loaves and use a spray bottle filled with water to heavily spritz the loaves. Place the loaves on a cornmeal-dusted wooden peel. With a razor blade or sharp knife, score the tops of the loaves with 5 uniform slices perpendicular to the length of the loaf.

Step 16

Slide the loaves onto the preheated baking stone. Add a few ice cubes to the heated cast iron skillet and cover the loaves with the upside-down large stainless steel bowl or aluminum roasting pan in order to capture the steam. Bake for 8 minutes. Then uncover the loaves and bake until the desired color has been achieved, roughly 30 to 35 minutes, although baking times will vary depending on the size of your loaves.

Step 17

Remove the loaves from the oven, place them on a wire cooling rack, and spray heavily with water. Let cool completely before cutting.