BLESS THIS MESS
Preheat the oven to 350°F. In a large mixing bowl, cream the butter and sugar together using an electric hand mixer. Cream the ingredients on a high speed for 2-3 minutes, or until smooth.
Add the eggs and vanilla to the bowl. Mix again until the eggs are fully incorporated into the mixture.
Fold in the mashed banana until it is evenly distributed throughout the muffin batter. Gently whisk in the baking soda, ground cinnamon, and flour on a low speed until no clumps of dry ingredients remain.
Add your walnuts to the muffin batter and fold them in until they are evenly distributed. Line a muffin tin with liners and divide the batter among the liners.
Bake your muffins for 20 minutes, or until a toothpick can be cleanly removed from the center of the muffins.