Sift together flour, sugar, soda, baking powder, and salt. Add buttermilk and dissolved yeast. Add shortening and stir. Store dough, covered, in the fridge until ready to use.
Roll out on a lightly floured surface or shape into balls--these do not need to rise. Brush tops of biscuits with melted butter.
Bake at 400 degrees F (205 degrees C) for 15-20 minutes.