No need for a mixer for this recipe. Preheat the oven to 350F 175C. With 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 mix in. Add the flour last mix. Pour mixture into a buttered 4×8 inch loaf pan. Bake for 1 hour. Cool on a rack. Remove from pan and slice to serve.