Mix together water, yeast and 1 tsp sugar. Let stand for 5-7 minutes until foamy.
Mix together flour, 3 Tbsp sugar, baking powder, salt and baking soda. Cut in butter with a pastry blender until crumbly.
Add in yeast mixture and buttermilk and stir until dry ingredients are incorporated. Do not overmix
Cover bowl with plastic wrap and refrigerate for 2 hours up to 5 days.
Preheat oven to 400 F. Turn dough onto a lightly floured surface and knead a few times. Roll dough into a 3/4 inch rectangle, fold dough and repeat.
Roll out dough to 3/4 inch thickness and cut with a 2 inch round biscuit cutter.
Add 1/2 of melted butter to a 10 inch cast iron pan and place cut biscuits into pan.
Brush top of biscuits with 1/2 of melted butter.
Bake for 15-20 minutes or until golden brown. Remove from oven and brush with remaining butter. Sprinkle with coarse salt.
Video
Notes
If working with yeast scares you, I put together a great post where I walk you through how to work with yeast. This will help guarantee your biscuit making is a big success.
Don't skip the melted butter and sprinkle of flaky sea salt on top. The butter makes them golden brown and the salt makes these skillet biscuits extra delicious.