1. Preheat oven to 350 degrees F. Coat a 12-cup muffin pan with nonstick spray.
2. Sift the flour, sugar, baking soda and salt together.
3. Whisk together the eggs, buttermilk and bran flakes. Let stand for 10 minutes.
4. Make a well in the center of the dry ingredients and add the egg mixture all at once. Stir with a wooden spoon until the dry ingredients are just moistened.
5. Fold in the mashed banana, taking care to keep the mixing to a minimum; some lumps are fine. Fill the muffin tins two-thirds full.
6. Bake in the prepared muffin tins for about 25-30 minutes. The muffins are done when a paring knife inserted in the center of the muffins comes out clean.Serving Size: 1 muffin