Dough: plain sourdough, 440 g flour, 1 tsp salt, 2 tsp sugar, 1 tsp dry yeast, 45 g butter, 22 g milk powder, 280 g water.
Mix everything into a soft dough.
Leave for autolysis for 15 minutes. You may have to add flour or water – look at the consistency of the dough, it should be quite soft, sticky.