Preheat oven to 350°F and grease a 12 capacity muffin pan.

In a large mixing bowl, by spoon, mix butter into mashed bananas.

Mix in sugar, egg and vanilla.

Sprinkle salt and baking soda over mixture and mix.

Add flour and stir until incorporated.

Fold in nuts (optional).

Pour into muffin pan and bake for 20-25 minutes.

Remove muffins from pan and cool on wire rack.