• Preheat oven to 375F (regular bake/not fan-assisted). Grease a muffin pan (about 9 muffin cups) with baking spray or oil or you can line with muffin liners. Set aside.

Make the crumb topping:

• In a small bowl, stir together the brown sugar, flour and cinnamon until well mixed. Add the butter, broken into 4 chunks or so. Using your fingertips, rub the butter into the flour/sugar mixture until you have an even crumb, similar to coarse cornmeal. Pop the bowl into the fridge while you make the muffin batter.

Make the muffin batter:

• In a large bowl, whisk together the banana, white sugar, brown sugar, egg, oil and vanilla. Set aside.
• In a medium bowl, whisk together the flour, baking soda, baking powder, salt, nutmeg and cinnamon.
• Add the flour mixture to the egg/banana mixture all at once, then using a spatula or spoon, stir the mixture together just until the flour is no longer visible. Don't over-mix.
• Using a spoon or a scoop, divide the batter between 9 muffin cups. They should be filled almost to the top, as shown in the photos above.
• Remove the crumb from the fridge and sprinkle over the batter. *You can add as much or as little as you like. The crumb does add a bit more sweetness to the muffins, so keep that in mind if you prefer a less sweet muffin. In any event, you probably won't need quite all of the crumb topping.
• Bake muffins for 18-20 minutes or until golden and they test clean when tested with a cake tester or toothpick. Let the muffins cool in pan 10-15 minutes, or until they easily release from the muffin cups. Remove muffins to a cooling rack to cool completely.
• Muffins are best enjoyed on the day they are baked, when the topping is nice and crispy. The topping will soften as they sit into the next day. I generally avoid covering them too tightly. These muffins will also freeze well up to 3 months.