Preheat oven to 375 degrees F (190 degrees C). Lightly grease 12 muffin cups, or line with muffin papers, set aside.
In a large bowl, combine 1 1/2 cups flour, baking soda, baking powder, nutmeg, cinnamon, and salt.
In another bowl, beat together bananas, sugar, egg and melted butter (or oil). Stir the banana mixture into the flour mixture just until moistened then spoon batter into prepared muffin cups.
In a small bowl, mix together brown sugar, flour and cinnamon and butter until the mixture resembles coarse cornmeal. Next, Sprinkle a generous layer of topping over muffins.
Bake in preheated oven for 18 to 20 minutes, until a toothpick inserted into center of a muffin comes out clean. Enjoy!