Sift the flour, baking powder, salt, and baking soda into a large mixing bowl.
Using a pastry cutter, two butter knives or your hands work the cold butter into the dry mixture until pea-size coarse crumbs have formed.
Next, add the sourdough starter and buttermilk or another dairy you are using to the bowl. Mix until a dough forms. If it seems dry add a tiny amount of buttermilk to the bowl. (See notes on sourdough starter)
Turn the dough out on to a floured surface and knead about 5 to 8 times just enough so the dough is soft and pliable. Do not over-knead or your biscuits will be tough and not tender.
Roll out with a floured rolling pin to about ½ inch thickness. Use a round 2 ½ inch biscuit cutter or cookie cutter to cut the biscuits.
Place the cut out biscuits on a buttered baking sheet 2 inches apart. Brush melted butter over the tops.
Bake for 12 to 14 minutes in a 450 F. preheated oven until golden brown.
Makes 18 biscuits.
Do not over-knead or handle the dough.
Start with a very active sourdough starter
If your sourdough starter is very thick verses very thin you may need to add a drop or two more buttermilk to the dough.
The dough should be stiff,not sticky. Dust with flour well but the extra flour could make tough biscuits.