1. Preheat oven to 450°. Sift together first 4 ingredients in a large bowl. Cut butter into flour mixture with a pastry blender until mixture resembles small peas. Stir in buttermilk with a fork until dough forms a ball.
2. Turn dough out onto a well-floured sheet of wax paper. Sprinkle dough with flour, and flatten into a disk. Cover, and chill 15 minutes.
3. Remove wax paper, and turn dough out onto a well-floured surface; sprinkle with flour. Pat dough to 1/2-inch thickness. Cut with a 3-inch cutter, reshaping scraps once. Place biscuits 1 inch apart on an ungreased baking sheet.
4. Bake at 450° for 10 to 12 minutes or until golden brown. Brush immediately with melted butter.