1. Preheat oven to 425 degrees F. Line a standard muffin tin with paper cups.
2. In a large bowl, whisk together the oat bran, baking powder and brown sugar. In a separate medium bowl, mix together the milk, mashed bananas, egg whites and agave nectar.
3. Add the wet ingredients into the dry ingredients and whisk until combined. Fold in the walnuts. Divide the batter evenly between the 12 muffin cups. Bake until the muffins are lightly browned and a knife inserted in the center comes out clean, about 12 to 15 minutes.
4. Cool the muffins in the pan for 5 minutes, then remove to a wire rack to cool completely. Store in an airtight container at room temperature. Serve at room temperature or reheat in the microwave and top with your favorite jam, butter or even peanut butter.