The first step in making bran muffins is to combine the bran cereal and milk, and let the mixture stand for 5 minutes.
Combine the flour and other dry ingredients in a large bowl, and make a well in the center of the dry mixture.
Next, combine the wet ingredients, in this case, banana, peanut butter, oil and an egg, and stir well. Stir the banana mixture into the cereal mixture, then add that wet mixture to the dry mixture, stirring just until moistened. The less the muffin batter is stirred, the better. If you overstir, you end up with tough muffins that have tunnels inside.
Spoon the muffin batter into muffin pans that have been greased or coated with cooking spray. Fill them about two-thirds full. If all of the muffin cups aren’t filled up with batter, pour water into the empty cups before baking to keep the cups from buckling.