Combine whole wheat flour and butter in a mixer bowl. Mix until crumbly. Add milk and sourdough starter. Mix well. Place in a bowl, cover tightly and refrigerate for 24 hours. Remove from refrigerator. *Sprinkle baking powder, salt, and baking soda on biscuit dough. Knead until thoroughly mixed. **Press dough out ½ inch thick, fold in thirds, press out again, repeat from * twice. Cut with a biscuit cutter and place on a baking sheet. Bake at 425 degree for 20 minutes or until lightly browned.