Preheat oven to 350 and line + spray a 12-muffin tin. Make flax egg, if using. Allow to gel in the fridge for 5 minutes while you prep the banana and rest of the wet ingredients. Mash bananas in a bowl and add the rest of the wet ingredients and mix well. Fold in dry ingredients. Bake for 15 minutes. Remove and let cool for a couple minutes. Enjoy immediately, or store in fridge for a week. Store in freezer for a few months.