Heat oven to 375℉.
In a medium mixing bowl, cream together the 1/2 cup of soft butter and 1 cup sugar until smooth. Add 1/2 teaspoon of vanilla, 1 cup of mashed bananas, 2 eggs, and 1/2 cup of chopped walnuts. Mix thoroughly.
In a separate bowl, mix together 1 teaspoon of baking soda, 1/2 teaspoon of salt, and 1 1/2 cups of flour. Add the combined dry ingredients to the wet ingredients and mix until all the flour is combined.
Spoon 1 1/2 tbsp of batter into cupcake liners. Aim to fill the liners no more than 2/3 full or they will over flow when they bake. Top with more finely chopped walnuts.
Bake for 20 to 25 minute or until golden brown and a toothpick stuck in the middle comes out clean.
Cool completely before eating.