At least 7 hours before baking the biscuits, prepare the dough for a long fermentation.
Cut the fat into the flour until it is in small pieces.
Stir in the sourdough start, sweetener, and milk until a soft dough just comes together. Cover and place in a warm spot to ferment for 7-12 hours
Preheat the oven to 400 degrees
When ready to begin baking, combine salt, baking powder and baking soda in a very small bowl evenly mixed.
Sprinkle mixture over the fermented dough and knead until it comes together into a cohesive, soft mass.
Roll the dough out to 1/2 inch thick.
Cut with 2-3 inch biscuit cutter and place the biscuits in a 10 inch oen-proof skillet, one next to another.
Place the skillet in the hot oven and bake for 20-30 minutes or until golden brown on the top and bottom.