Dissolve yeast in warm water. Sift dry ingredients. Cut in shortening, add buttermilk and yeast mixture. Knead on floured board about a minute. Roll to 1 cm 1 cm and cut in rounds. Bake at 200ºC or 10 minutes on greased pan. Place close together. Dough can be kept in refrigerator up to a week covered. Best to let rise slightly.