from Joy the Baker
3 cups all-purpose flour
2 Tablespoons sugar
4 1/2 teaspoons baking powder
3/4 teaspoon cream of tartar
3/4 teaspoon salt
1/2 cup shortening, cold and cut into cubes
1/4 cup butter, cold and cut into cubes
1 egg, beaten
3/4 cup buttermilk, cold
In a mixing bowl, sift together flour, sugar, baking powder, cream of tartar and salt. Cut in shortening and butter until mixture resembles coarse meal. In another bowl, combine egg and milk and beat lightly with a fork. Add to flour mixture all at once, stirring enough to make a soft dough.
Turn out onto a floured board and knead about 15 times. Roll or pat out into a 1-inch thickness. Cut into 2-inch rounds using a biscuit cutter or cut into 2×2-inch squares. Reshape and roll dough to create more biscuits with excess scraps. Place on an ungreased baking sheet and bake at 425 degrees F for 12-15 minutes. Serve immediately.