Preheat the oven to 350°F. Line two 8-inch loaf pans with parchment paper so that there is an overhang on the longer sides of the pans. Grease the parchment paper with cooking spray.
In a medium bowl, stir together the cake mix, oil, eggs, mashed bananas and sour cream until combined. Stir in 3/4 cup chocolate chips then divide the batter between the two prepared loaf pans. Sprinkle the top of each loaf with the remaining 1/4 cup chocolate chips.
Bake the bread for about 45 minutes or until a toothpick inserted comes out clean. Remove the loaves from the oven and transfer them to a rack to cool completely. Once cooled, use the parchment paper overhangs to lift the loaves out of the pans then slice and serve.
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