Preheat oven to 425 degrees F.

In a large bowl, combine flour, baking powder, salt, and baking soda.

Cut in butter until mixture resembles course crumbs.

Add sourdough starter and buttermilk to the flour mixture; stir with a fork until the dough forms a ball.

You may need to adjust the flour or milk depending on how thin your starter is.

Turn dough onto a well floured surface; knead 5-10 times.

Roll or pat out to 1/2 inch thickness.

Cut with a floured biscuit cutter.

Place 2 inches apart on a buttered baking sheet.

Brush with melted butter.

Bake in preheated oven for 12-15 minutes or until golden brown.