Prepare skillet with cooking spray and heat on medium until hot. In a mixing bowl, combine flours, cornmeal, oatmeal, brown sugar, baking soda, and salt. In another mixing bowl, combine egg whites, buttermilk, and sour cream. Mix dry ingredients with wet ingredients just until moistened. Ladle in the batter, using 3 or more tablespoons per cake. Cook for 2 minutes, then flip carefully and cook for 2 minutes more. Repeat with remaining batter.