Heat oven to 400°F. In a large bowl, combine flours, oats, sugar, baking powder, baking soda, cinnamon, and salt. In a separate bowl, beat together buttermilk and egg; add to flour mixture, and mix to combine. Stir in millet cereal, apple, and cranberries or raisins.
Divide batter among paper-lined muffin pans. Sprinkle granola on tops, if using, and bake 16 to 19 minutes or until center is firm.
