"Leftover Banana" Muffins

You know that banana that gets forgotten, only to be noticed a few days later when it's black? This is a recipe dedicated to that banana.

2 cups flour

1/2 cup sugar

2 teaspoons baking powder

1/2 teaspoon baking soda

1/2 teaspoon salt

1/4 teaspoon cinnamon

1 (or 2) meduim banana, mashed

1/2 cup milk

1/3 cup oil

1 egg, slightly beaten

Combine the first group of ingredients. Add remaining ingredients and stir only until moistened. (Over-mixing makes the muffins tough!) Spoon into lined muffin bans, and bake at 375° for 15-20 minutes.