In a heat-safe bowl, combine 75 g Bob's Red Mill 5 Grain or 7 Grain Hot Cereal and 120 g boiling water. Stir until evenly combined, cover, and allow the porridge to cool completely before using.

In a large mixing bowl, combine 250 g lukewarm water and 20 g honey. Stir until the honey begins to dissolve.

Add 350 g bread flour and 50 g whole wheat flour. Mix until no dry flour remains. The dough will look shaggy.

Cover and let the dough rest for 30 minutes.

Add 82 g active sourdough starter, 13 g salt, and all of the cooled multigrain porridge. Mix until everything is fully incorporated, then continue mixing vigorously by hand for 6–8 minutes until the dough becomes smoother.

Cover and let the dough rest for 30 minutes.

Perform 4 rounds of stretch and folds, allowing the dough to rest 30 minutes between each round.

Allow the dough to bulk ferment until it has almost doubled in size, usually takes 4–8 hours.

Turn the dough out onto your work surface and gently pre-shape it into a round. Let the dough rest uncovered for 15 minutes.

Shape the dough into a tight round and place it seam-side up into a lined banneton. Cover and refrigerate for 8–18 hours.

Preheat your oven to 450°F (232°C) with a Dutch oven inside for 30–45 minutes.

Turn the cold dough onto parchment paper, score the top, and lightly spray the surface with water.

Carefully transfer the dough to the hot Dutch oven using the parchment paper. Bake 20 minutes covered, then 20 minutes uncovered.

Allow the loaf to cool for at least 2 hours before slicing.