Mix Dry Ingredients: Combine flour, baking soda, baking powder, salt, and cinnamon in a bowl and mix until well combined
Prepare Bananas: Mash two overripe bananas in a separate bowl until they are smooth
Mix Wet Ingredients: Add sugar, egg, melted butter, milk, and vanilla extract to the mashed bananas. Mix until combined
Combine Batter: Add the dry ingredients into the wet mixture. Stir until just combined- do not overmix
Add Nuts: Fold in chopped nuts
Prepare Pan: Lightly grease a muffin pan with butter to add flavor and help with browning
Fill and Bake: Add the batter to the pan and bake in a preheated oven at 350°F for 18 to 22 minutes
Test for Doneness: Insert a toothpick into the center of a muffin; if it comes out clean, they are done
Cool: Let the muffins sit in the pan for about 5 minutes before removing them
