Preheat the oven to 400. Line a muffin tin with muffin liners.
In a small bowl, crush the bran cereal and add the buttermilk. Set it aside to soak.
In a medium bowl mix together all the remaining dry ingredients.
In a large bowl combine the egg, brown sugar, oil, mashed banana, and vanilla. Mix until combined.
Add the dry ingredients and buttermilk mixture into the large bowl and stir until just combine. Fold in the blueberries / raspberries -- don't over mix.
Using a cookie scoop, divide the batter into the prepared muffin cups. Bake for 20 minutes or until a toothpick comes out nearly clean.
Let muffins cool for 5 minutes in pan and then take out of pan and let cool completely. Enjoy!