Dissolve yeast in water. Sift flour and remaining dry ingredients together in large mixing bowl. Add shortening, buttermilk, and yeast; mix well. Turn out onto floured board; knead well. Cover; refridgerate. When ready to bake, pinch off as much dough as needed. Return remaining dough to refridgerator. Roll out the amount you are using to about 1/2" thickness. Let sit in pan to rise for 15-20 minutes. Bake in 375 degree oven until brown, about 20-25 minutes. Makes 5 dozen.