Preheat the oven to three hundred and fifty degrees. Grease a loaf pan and line with parchment paper.
In the bowl of a stand mixer, add two cups of mashed bananas, one-half cup of vegetable oil, one and one-quarter cups of buttermilk, two eggs and two teaspoons of vanilla extract. Mix until well combined.
Add two cups of Bisquick, one-half cup of sugar and one teaspoon of baking soda and continue mixing until all ingredients are well incorporated.
Stir in one-half cup of walnuts.
Pour the batter into the prepared loaf pan and bake for approximately one hour.
Transfer the bread to a cooling rack. Slice and serve with warm butter. Enjoy!