Prepare your oven and loaf pan: Preheat oven to 350 F degrees. Spray a 9x5-inch loaf pan with cooking spray or grease it with butter.
Combine dry ingredients: In a medium bowl add the flour, baking soda, salt and mix together; Set aside.
Combine the wet ingredients: In another large bowl, add sugar and butter and beat with a mixer at medium speed until well incorporated. Add eggs, and sour cream; beat until blended then stir in mashed bananas.
Combine the dry and wet: Add flour mixture; beat at low speed just until moist.
Melt chocolate chips: Place chocolate chips in a medium microwave-safe bowl, and microwave at high for 1 minute or until almost melted. A minute was enough for me, stir until the chocolate is smooth.
Make chocolate batter: Add 1 cup of the batter to the chocolate and stir so that it's well combined.
Spoon into loaf pan: Spoon the white batter first in the greased pan, then the chocolate batter, and swirl batters together with a knife. Or first spoon a layer of white batter, then a layer of chocolate batter, then white batter, then chocolate and if there's any white batter add it on top.
Bake: Bake for about 1 hour to 1 hour and 15 minutes or until an inserted toothpick in the middle of the bread comes out clean.
Cool and serve: Cool for 10 minutes in the pan, then remove from pan and continue cooling on a wire rack. Slice and serve.