Preheat oven to 325 degrees. Grease two light colored loaf pan (8 1/2" x 4 1/2" x 2 3/4” high) with non-stick cooking spray and line the bottom and longest sides with parchment paper. Spray lightly again with cooking spray and set aside.
In a large bowl, mix butter and sugars until well combined. Stir in eggs, vanilla, and banana until smooth. (It may turn a little lumpy, but this is completely normal.)
Gently stir in dry ingredients and sour cream until a uniform batter has formed. Scrape sides to ensure no lumps are present. Stir again briefly if needed. Fold in 1 1/2 cups of chocolate chips into batter. Divide evenly between prepared pans. Top each loaf with 1/4 cup chocolate chips (or more) if desired.
Bake for 50 to 60 minutes in the lower half of the oven or until completely baked. If your loaves are getting too dark for your liking, you can tent with foil. Remove from oven and cool at least 20 minutes before removing from pan. Slice and serve.