Preheat oven to 425°.
Heat a small skillet coated with cooking spray over medium heat. Add onion; cook 6 minutes or until tender, stirring frequently. Spoon onion into a blender. Add milk; process until smooth. Cool.
Lightly spoon flours into dry measuring cups, and level with a knife. Combine flours and next 5 ingredients (flours through basil) in a large bowl; cut in the butter with a pastry blender or 2 knives until the mixture resembles coarse meal. Add onion mixture; stir just until moist. Turn dough out onto a heavily floured surface (dough will be sticky), and knead lightly 5 times with floured hands. Roll dough to a 1/2-inch thickness; cut into 10 biscuits with a 3-inch biscuit cutter. Place on a baking sheet coated with cooking spray. Bake at 425° for 12 minutes or until golden.