In a large mixing bowl or stand mixer stir together yeast, flour, baking powder, baking soda, salt and sugar. Cut in the butter or shortening until the mixture resembles coarse crumbs.
Stir in the water and buttermilk until smooth. Turn onto a floured surface and knead a few times. At this point you can roll out and cut the biscuits, or refrigerate the dough in a covered container for 1-3 days.
Roll out the dough to about ½ inch thick. I usually just use my hands to press the dough out into a square (1/2 inch thick) then I cut the square into 16 pieces. I combine the corner pieces together, to make about 14 even sized biscuits. I find this faster and easier than cutting out with a round biscuits cutter, but either method works great!
Place cut out biscuits in buttered cast iron pan, or a parchment-lined baking sheet. Brush the tops of the biscuits with melted butter. Cover lightly with plastic wrap and allow to rest for 30 minutes.
Preheat oven to 425 degrees F. Uncover biscuits and bake for about 13-18 minutes, until golden brown.
Make Ahead Instructions: Angel biscuit dough will keep, covered well, in the refrigerator for 1-3 days before resuming with cutting and baking.Freezing Instructions: Dough for Angel Biscuits can be wrapped up and stored in a freezer-safe container for up to 3 months. Thaw overnight in the refrigerator, then form and bake as directed. Baked and cooled biscuits can be frozen in a freezer-safe container for up to 3 months. Thaw overnight in the refrigerator and rewarm for a few seconds in the microwave.