These little gems are a big hit in my house. I topped the ones pictured with pink sugar for a party, but that is optional. I do recommend it because it gives them a little sweet crisp on top. You can use any color or just plain white suger.
In a large bowl whisk together the flour, baking soda, baking powder, salt, cinnamon and nutmeg. Make sure these are fully incorporated and set aside.
In the bowl of a stand mixer with the paddle attachment or a hand held mixer, mash bananas. Add white and brown sugar and mix. Add eggs and mix. Then add the melted butter and vanilla extract and mix well. I ALWAYS use real butter so I would not recommend using margarine as this will change the taste and texture and overall quality of the muffins.
Slowly add the dry ingredients into the wet ingredients using a scoop or cup mixing between each addition. Mix on low until fully incorporated, scraping down the sides if needed. Do not overmix as this will result in tough muffins. Mix just until all the flour mixture is incorporated with the wet ingredients.
Preheat oven to 350 degrees. Line a muffin pan with papers and spray each paper with a little cooking spray. Fill each paper about 2/3 full. Sprinkle each muffin with colored or white sugar (optional) and bake for 20 to 25 minutes or until a tooth pick comes out almost clean when inserted. Let cool on cooling rack and store covered.