Heat oven to 425°. In a large bowl, mix flour, salt, sugar and baking powder (if using). Add butter and blend in using fingers. Form a hollow in the flour mixture and pour in 2 cups sourdough starter. Using a fork, slowly mix starter around until it has picked up all of the flour. You should have a soft, pliable dough. Add a couple teaspoons water if needed. Mix well.

Pinch off balls about the size of an egg (2½ ounces each) and pat into rounds ½ inch thick. Butter a 9-inch cast-iron skillet and fill with the rounds with the edges of the rounds touching. Brush with melted butter.

If you add the baking powder, you can bake these right away. Otherwise, cover lightly with plastic wrap and let rise in a warm, draft-free place for 2½ hours. Either way, bake for 12–15 minutes, until lightly browned. Brush with melted butter. Let them cool a few minutes and then enjoy your handmade wildly fermented locally grown heritage-wheat biscuits. And pass the butter, please.

*Note: Baking powder is an optional convenience in this recipe, but it's been around since the 1840s. If you add the baking powder you can bake the biscuits right away, and the sourdough flavor will be much milder. Before baking powder, cooks let their biscuits sit a few hours to rise before baking, which develops a delicious tang. For authentic sourdough biscuits without baking powder, let the dough rise at least 2½ hours before baking.