Combine flour, baking powder, salt, and soda in a large mixing bowl; stir well. Cut in shortening with a pastry blender until mixture resembles coarse meal. Combine buttermilk and egg, beating well; gradually add to dry ingredients, stirring just until moistened.
Turn dough out onto a lightly floured surface, and knead 10 to 12 times.
Roll dough to 1/2-inch thickness; cut with a 1 1/2-inch biscuit cutter. Place biscuits on a lightly greased baking sheet. Bake at 450° for 12 minutes or until lightly browned. Serve hot.