12 hours before you plan to mix the dough, add the ingredients to make ½ cup (100 g) of active sourdough starter to a clean jar. Stir until combined, loosely cover the jar and let the starter rise at room temperature. (The ingredients will create a total of 115 g active starter but, because some of it will stick to the sides of the jar during the transfer, we are making a little more than needed.) The sourdough starter is ready to use when it has doubled in size and there are plenty of bubbles on the surface and sides of the jar.

Mix the dough: In a large mixing bowl stir together 100 grams of active sourdough starter, 375 grams of water, and 10 grams of salt. (This step will ensure the starter is evenly distributed throughout the dough.) Next add 50 grams of whole wheat flour, 50 grams of rye flour, and 400 grams of bread flour to the bowl. Use your hands to combine the ingredients until there are no dry bits and the dough looks like a shaggy mass. Cover the bowl and let the dough rest on the counter for 1 hour.

Prepare walnuts and raisins: While the dough is resting, prepare the raisins and walnuts. Bring a small pot of water to a simmer and turn the burner off. Add ½ cup of walnuts and ½ cup of raisins to the pot, making sure they are covered by the hot water. Allow them to sit in the hot water until it's time to mix them into the dough.

Stretch and fold: Perform one set of stretches and folds to the dough. To perform a set, while the dough is still in the bowl, pick up one side with a wet hand. Pull it up and over itself. Turn the bowl and repeat this action on 4 sides of the dough until the bowl has come full circle. Cover the bowl and let the dough rest for 30 minutes.

Add walnuts and raisins to the dough: Drain the water from the raisins and walnuts and then add them to the bowl of dough. Use your hands to mix them into the dough until they are evenly incorporated. Cover the bowl and let it rise 30-50% at room temperature, 3-5 hours depending on the temperature of your kitchen.

Prepare butter spread: Right before the dough is ready to shape, mix 4 tablespoons of softened butter with ¼ cup of brown sugar, 2 teaspoons cinnamon, ½ teaspoon vanilla extract, and a pinch of nutmeg. Set aside.

Spread butter mixture on the dough: Turn the dough out onto a floured work surface. Use your hands to press the dough out into a 12 x 10"rectangle. Flour your hands to prevent the dough from sticking. Spread the butter mixture over the dough being careful to keep it 1-1 ½ inches from the edges.

Shape the dough: Pick the right side of the dough up and fold it towards the center and repeat with the left side. Pick the top side up and fold it towards the center and repeat with the bottom side. Fold the dough in half and then flip it over so that the seam-side is facing down. Pull the dough towards you while turning it to create a taut skin on the outside. Dust flour on the outside of the dough and flip it into a lined banneton that has been floured. Cover the banneton with plastic wrap. (I use a reusable shower cap.)

Second rise: If you'd like to bake the same day, allow the dough to continue to rise at room temperature until it has reached the top of the banneton. For a long ferment, let the dough sit on the counter for 30 minutes before placing it in the fridge overnight.

Bake: Preheat your oven to 450°F (232°C) with a dutch oven inside. Once the oven is hot remove the dutch oven and set it on top of the stove. Turn the dough out onto a piece of parchment paper. Use a razor to make 3 very shallow slits across the top of the dough. Using the parchment paper as a sling, lift the dough up and into the dutch oven. Bake covered for 30 minutes and uncovered for 20 minutes.

Cool: Place a cooling rack onto a piece of parchment paper or baking sheet. (This will catch any melted butter that may drip from the baked loaf.) Transfer the loaf to the cooling rack and allow it to cool completely.