In a medium bowl, mix together the buttermilk and starter together.

In a large bowl whisk together the flour, salt, baking soda, and baking powder.

Cut the cold butter into the dry ingredients until it looks like cornmeal or sand.

Combine the buttermilk/starter into the dry ingredients and mix until a soft dough forms and it comes away from the side of the bowl. Do not overmix.

Turn the dough out onto a floured surface and carefully knead to ensure it is all mixed together, but do not over knead. Just two or three times is good.

Gently pat into dough out until it is 1/2" thick.

Fold the dough over on itself into thirds (like an envelope) and gently pat out again until it is 1/2" thick.

Repeat folding the dough over onto itself in thirds and then pat out with your fingers until the dough is 1/2" to 3/4" thick again. This will help to create layers in the biscuits.

Cut biscuits and place on a lightly greased baking sheet.

You can use your hands to gently bring any scraps together and repress to continue cutting out biscuits, but try not to overwork the dough. The more you handle the dough, the tougher your biscuits will be.

Cover with a towel and let rest for 30 minutes (I have also successfully skipped this step several times and they turn out just fine - not as high as the rested ones, but they still have good layers and flavor).

Brush the tops of the biscuits with melted butter.

Preheat the oven to 425F.

Bake for 10-15 minutes or until the tops of the biscuits are golden brown.