In a large mixing bowl, the night before you want to eat these delicious sourdough biscuits add in your flour, cup sourdough starter, milk, and butter into a large glass bowl, and mix well. Cover it with a tea towel and let it ferment for 8-12 hours. The melted butter will get to room temperature and the wild yeast will work its magic for the biscuit dough.
The next morning add in your flour mixture with the dry ingredients to your fermented biscuit dough that was left to rise overnight in the large glass bowl. The dry ingredients are flour, baking soda, baking powder, sugar, and salt.
Once both the wet and dry ingredients are mixed well together, take the dough out of the bowl and place it on a well-floured clean work surface. Roll the dough out to your thickness preference and cut with a biscuit cutter, mason jar, or even a cute cookie cutter of choice. I prefer about ½ to 1 inch because they puff up in the oven to about a 2-inch thickness.
Add the biscuits to a well-greased baking sheet (I also love using a Silpat or even parchment paper). Bake biscuits at 400 degrees for about 15 minutes or until they are golden brown.