Step 1Stir together flour, baking powder, salt, baking soda and sugar in large bowl. Cut butter and shortening into dry ingredients until crumbly and well distributed.
Step 2In small bowl, sprinkle yeast over warm water and stir briefly. Allow to dissolve and swell, 5 to 10 minutes. Add yeast mixture and warm buttermilk to dry ingredients and toss with a fork to blend and moisten. Cover bowl and refrigerate overnight or up to 2 days.
Step 3To make biscuits, roll dough out on lightly floured board to a thickness of 1 inch or so. Cut into rounds, wedges or squares with a knife or biscuit cutter. Brush generously with melted butter.
Step 4Place on baking sheet. Bake at 400 degrees until lightly browned on top, about 12 to 15 minutes.