4 cups flour
8 teaspoons baking powder
½ teaspoon baking soda
1 1/2 teaspoon salt
4 tablespoons butter
4 tablespoons shortening
2 cup buttermilk, chilled

Preheat oven to 450 degrees.

In a large mixing bowl, combine flour, baking powder, baking soda and salt. Using your fingertips, rub butter and shortening into dry ingredients until mixture looks like crumbs. Make a well in the center and pour in the chilled buttermilk. Stir just until the dough comes together. The dough will be very sticky.

Turn dough onto floured surface, dust top with flour and gently fold dough over on itself a few times.  Don't overwork the dough or it will be tough. Press into a 1-inch thick round. Cut out biscuits with a biscuit cutter or drinking glass (like my mother always did), being sure to push straight down through the dough.  Place biscuits on pizza stone so that they just touch. Reform scrap dough, working it as little as possible and continue cutting.

Bake until biscuits are tall and light gold on top, about 15 minutes. Brush with melted butter.