Preheat oven to 350 degrees F. Line a muffin pan with cupcake liners, or grease with nonstick spray.

Combine the flour, sugar, baking powder, baking soda and salt in a large bowl. In a separate bowl combine the butter, egg, milk, vanilla, and mashed bananas. Add the banana mixture to the flour mixture until just combined. Do not over mix. Fold in the walnuts, granola, and coconut.

Fill prepared muffin pan to about 3/4 full with batter. Sprinkle with additional walnuts, granola, and coconut if desired.

Bake for 25 minutes or until a toothpick inserted into the center comes out clean. Let cool in the pan until just cool enough to handle, then transfer to a wire rack to cool completely.