Preheat the oven to 400°. Spray a 12-cup nonstick muffin pan with oil. In a large bowl, whisk the flour with the oat bran, brown and granulated sugars, baking powder, baking soda, salt and cinnamon. In a food processor, puree the ricotta with the buttermilk. Add the milk, melted butter, vanilla, egg and egg white and pulse until smooth. Add the bananas and pulse just until blended.
Using a rubber spatula, fold the banana mixture and 1/2 cup of the walnuts into the dry ingredients. Spoon the batter into the muffin cups and sprinkle the remaining 1/2 cup of walnuts on top. Bake the muffins for about 18 minutes, or until a toothpick inserted in the center of one comes out clean. Turn the muffins out onto a wire rack to cool.
One Serving Calories 256 kcal, Total Fat 10.9 gm, Saturated Fat 2.6 gm.