Dissolve yeast in water, set aside. Mix dry ingredients in order given; cut in shortening until the size of small lima beans. Stir in buttermilk & yeast mixture. Cover bowl with towel & let sit until ready to use. (Atleast 1 hour, but it is fine if it sits for a couple hours.) Dough will be very sticky. Scrape out onto well floured board. Flip over & knead lightly (4-6 times). Roll out & cut with biscuit cutter. Place on greased pan & let raise slightly (10-30 minutes). Bake at 400° F until light brown, 10-12 minutes.