Making a Sourdough Starter

Dissolve 2 tbsp/15 g fresh yeast or 1 tbsp/7 g active dry yeast in ¼ cup/60 ml water and 1 tsp sugar. Stir in 2 cups/500 ml warm water and about 2 cups/250 g unbleached all-purpose flour—enough to obtain a thick but pourable batter. Cover the starter with a damp cloth and set it in a warm, draft-free place. Let it ferment at room temperature for three to five days before using. Commercial sourd