Updated: Jan 12, 2020
I like to use cocoa powder to get a nice dark color, eschewing any food coloring. The cocoa powder also works as a great complementary flavor for the rye flour and caraway crust.
What You'll Need (Levain Mix - makes more than you need) 80 grams mature sourdough starter
50 grams King Arthur Organic Whole Wheat Flour
150 grams King Arthur Organic Bread Flour
160 grams warm water
What you'll need
700 grams King Arthur Organic Bread Flour
300 grams Ardent Mills Organic Light Rye Flour
20 grams Kosher Salt
200 grams levain (see build below)
150 grams cocoa powder
Up to 780 grams warm water
Cornmeal for dusting
Caraway Seed for dusting (optional)
If you don't have a mature sourdough starter, check out my simple five-day process on creating one from scratch. I usually will mix with a fork or with my hand.
What You Need To Do
Dissolve the 200 grams of levain into 90% of the water. Add all of the flour and mix until just incorporated. Make sure there is no dry flour.
Let this mixture rest for anywhere between 15 minutes and 1 hour.
Divide the dough in half. If machine mixing, keep one half of the dough in the mixer. If hand mixing, you'll need two separate bowls for each half of the dough.
Add 10 grams of salt and 5% of the remaining water to each half of the dough. In only ONE half, add ALL of the cocoa powder.
Mix the dough without cocoa powder first for about 6 minutes if machine mixing and probably 12 minutes if hand mixing. Repeat the mixing process with the cocoa powdered dough. Be sure to clean your hands off when going from the cocoa powder dough to the other. The key is to end up with two distinctly different colored doughs before beginning bulk fermentation.
You'll want to achieve the same consistency in the dough that has the cocoa powder, so this might mean adding less or more water. It will all depend on your environment. Pay attention to your ending consistency in the first dough and try to get as close as possible with the second dough.
Transfer both doughs to the same tub when they are both developed and have the same consistency. You can put one right on top of the other.
Every 30 minutes, complete a stretch and fold. You'll start to notice a bit of the marbling takes place around the 3rd fold.
Allow the bulk fermentation to finish, for up to 5 hours. The dough should be slightly bubbly and smooth.
Divide the dough in half when your bulk is complete. Pre-shape each half into a round ball, applying a gentle amount of tension. Let sit for about 15 minutes.
Prepare a mixture of cornmeal and caraway seeds.
Give the dough a final shape by either rolling into a log or "stitching" it up. You can find examples of my shaping methods on my Instagram feed.
Roll the dough in the cornmeal/caraway mixture and then place in your proofing basket with the seam side up.
Put a plastic bag over each basket and place into the fridge for 12-15 hours.
You can bake these in cast iron pans or on pizza stones. Preheat either of these items with the oven to 500 degrees. By the way, I use the Ooni pizza stone as it is designed to withstand high heat. I've had plenty of cheaper stones crack at 450 degrees.
If using the cast iron, no need to spray the oven or add extra steam. If using the pizza stone, use a spray bottle after loading your bread into the oven and spray the sides and back.
You can lower your oven to 475 or 450 depending on your oven. Bake the loaf for 20 minutes on the stone/in the cast iron.
Let the steam out and then transfer your loaf to the top rack for another 20 minutes. I like to bake dark, so sometimes I go a little extra. I finish my bake with the oven door open to let all the moisture out.
You can let it cool or cut into it as soon as you can touch it without burning yourself.