Using a wooden spoon, mix butter into the mashed bananas in a large mixing bowl.
Mix in the sugar, egg, and vanilla.
Sprinkle the baking soda and salt over the mixture and stir.
Add optional walnuts and chocolate chips, if desired.
Add the flour and then mix by hand.
Spoon batter equally into muffin pan.
Sprinkle a little raw sugar to the top of the muffins.
Bake for approximately 20-24 minutes. Check to see if muffins are done by inserting a knife in the center of the muffin. If the knife comes out clean, muffins are done.