Dissolve yeast in warm water in a small bowl; let stand 5 minutes. Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, 3/4 cup cornmeal, and next 4 ingredients (sugar through baking powder) in a large bowl; cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal. Add yeast mixture and buttermilk; stir just until moist. Cover; chill dough at least 2 hours or overnight.
Preheat oven to 450°.
Turn dough out onto a lightly floured surface; knead 5 or 6 times. Roll dough to 1/2-inch thickness; cut with a 2 1/2-inch biscuit cutter into 32 biscuits. Place on 2 ungreased baking sheets. Coat tops of dough with cooking spray; sprinkle tops evenly with 2 teaspoons cornmeal. Let stand 20 minutes. Bake at 450° for 12 minutes.