Preheat the oven to 350°F with a rack in the middle. Butter a 9-x-13-inch baking pan or 12-inch cast iron skillet.

In a large bowl, dissolve the yeast in the starter. Whisk in 4 tablespoons of the sugar and let sit for 1 minute.

Whisk in the oil, baking powder, and salt. At this point, taste the starter. If it is too tart, add a little more sugar, to taste. Remember, the first time you use the starter, it will be the sourest.

Slowly begin stirring in the flour until it makes a soft dough and is no longer sticky. Turn the dough out onto a floured surface and roll out to about inch thick.

Cut out about 16 rounds with a biscuit cutter and place on the baking pan or skillet close together.

Cover the biscuits with a buttered piece of wax paper and let rise in a warm place for 40 minutes to 1 hour, or until nearly doubled in size.

Uncover the biscuits and bake for 20 to 25 minutes, or until golden brown. Brush with melted butter and serve warm.