– all-purpose flour – sourdough starter – milk – sugar – butter
Prepare the Dough Combine the flour, sourdough starter, milk, sugar, egg, and salt in a stand mixer. Mix on low speed until no dry flour remains.
Incorporate the Butter Add the butter gradually, one tablespoon at a time, waiting for each to fully incorporate before adding the next.
Knead the Dough Increase the mixer speed slightly and knead for about 20 minutes. The dough should be smooth, elastic, and pass the windowpane test.
Rest and Fold Cover the dough and let it rest for 30 minutes. Perform 2–3 sets of stretch-and-folds, spacing each set about 30 minutes apart.
Bulk Fermentation Let the dough bulk ferment at room temperature (around 72°F) until it rises about 50%.