Line muffin cups with  paper liners. And then lightly spray with  non-stick cooking spray.

Thaw the frozen bananas and mash them well with  a wooden spoon.

Add sugar, melted butter and vanilla extract and mix until well combined.

Stir in a lightly  beaten egg.

Add flour, baking soda, baking powder and salt. Mix until just combined.

If desired, add chocolate chips, or chopped nuts. And divide the batter into 16 muffin cups.

Bake the muffins at 375F for 18-20 minutes, or until inserted tooth pick comes out clean.