Preheat oven to 300 degree F.
With a mixer, cream together the butter, sugar and eggs.
Next, smash the bananas and add them to the butter mixture, mixing as you pour them in.
Add the sour cream, vanilla, cinnamon, salt, baking soda and flour to the butter mixture.
Mix just until the flour is incorporated. Don't overmix!
Pour batter into 4 greased loaf pans.
Bake at 300 degrees for 1 hour.
They are done when you can poke a toothpick or butter knife down middle of the loaf and pull it out clean, without any batter.
Let cook in pans for 5 minutes and then transfer the loaves to a cooling rack.
