Banana Muffins

1. Preheat oven to 400°F. Line or grease a muffin tin. (Note: the original recipe calls for a 325°F oven. Increasing the temperature of the oven while baking the muffins helps them to peak higher. Around 400° seems to do the trick.)
2. For the muffins, combine the flours, baking soda, baking powder, and salt in a large mixing bowl. In a separate bowl, mix together the mashed banana, sugars, egg, and melted butter.
3. Add the banana mixture into the flour mixture, and mix together until just combined. Make the topping in a separate bowl by combining the dry topping ingredients and cutting the butter into the mixture with the back of a fork.
4. Fill muffin liners about 2/3 full. Top with the crumble. Bake for 20 minutes.

(Recipe adapted from Blacksmith Inn.)