The Ultimate Banana Bread

Preheat the oven to 350°F.
In a large bowl, mix butter into the mashed bananas, using wooden spoon. Mix in the sugar, egg, and vanilla. Sprinkle the baking soda and salt over the mixture and mix in. Add the flour last, mix just enough to blend the ingredients.
Do not overmix.
Add chopped walnuts to the batter and mix them in to distribute evenly through the batter.
Butter a 4×8 inch loaf pan. Line the bottom of the pan with parchment paper, butter the parchment paper too. Pour the batter in the pan. Bake for 1 hour. Cool on a rack. Remove from pan and slice to serve.