Combine wet ingredients: In a large bowl, whisk together 280 grams strong brewed coffee (cooled), 100 grams water, 40 grams molasses or barley malt syrup, and 15 grams unsweetened cocoa powder until the cocoa is fully dissolved with no lumps.

Mix the dough: Add 400 grams dark rye flour and 100 grams bread flour to the wet mixture, stirring by hand until no dry flour remains. The dough will be thick, sticky, and dark—that's expected at 80% rye.

Add starter and salt: Dimple 100 grams active sourdough starter into the dough, sprinkle 11 grams fine sea salt over the top, and fold in until fully incorporated. Add 10 grams caraway seeds (optional) now if using.

Bulk ferment: Bulk ferment at 76–78°F. Check at the low end of the window—rye ferments faster than wheat. Look for a 40–50% rise, not doubling.

Load the pan: Grease a 9×5-inch loaf pan well. Scrape the dough in with a wet spatula and smooth the top with wet hands.

Proof: Proof at room temperature, or cold-retard in the fridge for up to 60 minutes for deeper flavor.

Preheat oven: Preheat oven to 450°F.

Bake: Bake at 450°F for 50 minutes, then reduce to 400°F and bake until the internal temperature reaches at least 205°F. Tent with foil if the crust darkens too quickly—rely on the thermometer, not visual color, since this dough starts dark.

Cool and rest: Cool in the pan for 240 minutes, turn out onto a rack, then rest at least 4 hours (ideally overnight) before slicing.