Heat your oven to 350 degrees and spray a 9x5" loaf pan with baking cooking spray or grease well with butter then set aside. Mash the bananas on a plate with a fork (it's easier to do this on a plate rather than a bowl) Set bananas aside.
In a large glass bowl (or other microwave save bowl) melt the butter for 40 seconds. It should almost be melted. Stir around until it's completley melted. Add the sugars and stir until combined.
Add the eggs, one at a time and stir until smooth. Add the vanilla and sour cream then the mashed banana. (To mash the banana, I ususally use a large dinner plate and a fork to mash them
Sprinkle the flour, baking soda & salt on top of the wet ingredients then fold the flour into the batter until just combined. If you are adding chocolate chips, do this now.
Pour into the prepared loaf pan and bake for 50 to 60 min. Check at 45 min. Bake until a toothpick comes out clean. Let rest for a few minuets to cool then turn onto a cooking rack to cool completely.