Muffins: Preheat oven to 350° F and lightly grease your muffin tin/baking cups with cooking spray.Muffins: Whip up bananas using the paddle attachment on your mixer for 3 – 5 minutes or until light and fluffy. It should end up being about 2 1/2 cups of banana fluff. Transfer to another bowl and set aside. Cream together the butter and brown sugar in the bowl of the mixer (there is no need to wash off the paddle or bowl from the bananas). Add eggs one at a time and then incorporate the whipped bananas until well blended. In a separate bowl combine flour, baking soda, and salt. Gradually add the dry ingredientsto the wet. Spoon batter into prepared cups. Streusel: Melt butter in the bottom of a medium microwave-safe bowl. Add the dry ingredients on top. IMPORTANT: Incorporate the dry ingredients with your FINGERS until the mixture is moist and crumbly. If you try to use a spoon it will congeal into one huge ball of goo. Drop the crumb topping onto the muffins and bake. 6 jumbo muffins: 20 – 25 minutes 12 standard muffins: 15 – 18 minutes