In a large bowl, combine flour, baking powder, salt and baking soda.
Use a pastry cutter or your hands to incorporate the butter until it resembles a coarse cornmeal.
Add the sourdough starter and ¼ cup of milk to the flour mixture.
Use a rubber spatula to mix until a dough begins to form.
Form the dough into a 1-inch thick rectangle or circle, and use a biscuit cutter to cut out the biscuits.
Bake at 450°F for 14-18 minutes or until golden brown.
Serve with honey, jelly, jam, or your other favorite spread.
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