1: Preheat oven to 400°. Grease muffin pan.
2: Combine flour, oats, brown sugar, chopped nuts, baking powder, and baking soda in a large bowl.
3: In a separate bowl, combine mashed bananas, melted butter, milk, and beaten egg.
4: Combine the wet ingredients into the dry ingredients until just combined.
5: Fill muffin cups 3/4 way full.
6: Combine 1 tablespoon melted butter with enough brown sugar and nuts to make a crumbly topping.
7: Sprinkle the topping over the batter.
8: Bake for 16-18 minutes.
