Day 1 (Morning): Feed sourdough starter

1. The morning of the day before you plan to make this loaf, feed your sourdough starter so that it is active and ready to go.

Day 1 (Evening): Prepare the levain

1. Prepare your levain the evening before you plan to make the dough.
2. Place the sourdough starter in a medium bowl and pour the stout over it. Stir to break up the starter. Add in the rye flour and mix the ingredients together until the flour is completely hydrated. Cover the bowl with plastic wrap, and let it ferment at room temperature overnight (8-12 hours, depending on your starter). The mixture will not double, but become fluffy and airy.

Day 2: Prepare the Final Dough

1. Combine wet ingredients (stout, water, sweet potato), and mix to break up the sourdough.
2. Mix in 500 grams flour, and all of the oats using a wooden spoon or Danish dough whisk, then wet hands to make a sticky dough. Add additional flour as necessary – up to 100 grams.
3. Cover the dough and let it autolyse (rest) for 30 – 60 min. (Allowing the dough to rest before adding the salt, helps the gluten begin to develop and keeps the dough from getting tough.)
4. After the autolyse, add the salt, and mix until fully incorporated. Add a few drops of water to helps dissolve the salt, if necessary.
5. Turn the dough out into a greased bowl. Perform a series of stretch/folds, then cover tightly with plastic wrap.
6. Let the dough bulk ferment in the bowl for 3-4 hours. Repeat stretch/folds every 30 min for the first two hours. After the first two hours, bulk ferment on the counter for an additional 1 -2 hours.
7. Turn the dough out onto the counter or wooden board, cover and bench rest for 10 min. Prepare a round banneton or linen-lined basket or bowl by dusting with brown or white rice flour. Shape dough into boule, and place in your banneton.
8. If you place the dough seam side down, when it is turned out into the Dutch oven, the seam should open up naturally in the oven without having to slash the dough. If you prefer to score the dough before baking, place the boule seam side up in the basket.
9. Place dough in a plastic bag or cover tightly with plastic wrap and cold ferment in the fridge (12 – 24 hours).

Day 3: Bake the Loaf

1. Preheat the oven to 500F (260C) for at least 40 minutes with a cast iron Dutch Oven on the middle rack. You’ll bake the dough directly from the fridge so don’t remove the proofing basket until you are ready to flip the loaf into the pot.
2. Carefully turn the dough out into a combo cooker or Dutch oven, slash (if your seam is down), cover and put in the oven.
3. Reduce temperature to 475F (245C) and bake covered for 25 minutes. After 25 minutes, carefully remove lid, reduce oven temp to 450F (232C), and continue baking for an additional 20-25 minutes, or until crust turns a dark chestnut brown. Don’t be afraid to bake strong for a dark flavorful crust.
4. Cool on wire rack 90 minutes before slicing.