Preheat oven to 400 degrees.
Mix all dry ingredients together with a fork, in a wide, large mixing bowl.
Grate the frozen butter (with a large grater) into the bowl. Add shortening. Next, "cut" in the butter & shortening with your fork until the mixture is crumbly.
Pour buttermilk into the middle of the bowl & blend biscuits until a somewhat sticky dough has formed.
Prepare surface with flour & roll out your biscuit dough until about 3/4" thick.
Place biscuits on a baking sheet & bake for about 12 - 15 minutes or until golden brown.