Dissolve yeast in warm water. Sift dry ingredients together, then cut shortening into the flour mixture. Add buttermilk and yeast. Knead lightly--do not let rise. Roll out and cut with a round biscuit cutter. Cut almost through center of biscuit with a knife and fold over to form a pocketbook shape. Bake for 20 minutes at 200ºC Brush with melted butter after baking.