Butter a muffins pan or place muffin/cupcake cups into a muffin pan.
In a large bowl, mash the bananas. Add melted butter, milk, sugar and mix with a fork or a spoon to combine. Add an egg and continue mixing until well-blended.
In a separate bowl, mix together flour, baking powder, and a pinch of salt. Add dry ingredients to the wet ingredients. Mix to blend the ingredients but do not over-mix.
Pour the banana bread muffin batter into the muffin pan. Bake for about 25 minutes. Cool on a rack. Remove from pan when cool enough to handle.