Preheat oven to 350F and prepare one large or two small loaf tins.
Combine all of the dry ingredients and set aside.
With a hand or stand mixer, cream softened butter and sugars until light and fluffy.
While still mixing, add the eggs one at a time, waiting for each to be well incorporated before adding the next.
Beat in the sour cream (or yogurt) and vanilla extract.
Beat in the mashed bananas.
Slowly incorporate the dry ingredients, mixing until just combined. Do not overmix!
Fold in the chocolate chips.
Pour into the loaf tins and bake for 60-75 minutes. Your banana bread is ready to come out of the oven when an inserted knife or toothpick comes out clean of batter. (Your knife/toothpick will have melted chocolate on it.)
Turn loaves onto a cooling rack and allow to cool. Loaves can be well wrapped up and frozen.