1. Melt one cup of chocolate chips. Set aside.
2. Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius). Line a 9×13-inch (23×33-centimeter) baking pan with Gefen Parchment Paper and set aside.
3. In a large bowl, mix together sugar, oil, water, vanilla, and eggs. Mix until nicely incorporated. Add flour, baking soda, and salt and mix well.
4. Divide the batter into two separate bowls. In one of the bowls, add the mashed bananas and mix until fully incorporated. In the other bowl, add the melted chocolate chips and the coffee. Mix well, then stir in the reserved 1/2 cup chocolate chips.
5. Alternately pour dollops of each batter into the pan. Once all the batter is in the pan, lightly marbleize the two batters using a knife or a toothpick. Alternatively, spoon into muffin cups and then marbleize.
6. Bake for 40–45 minutes (15–20 minutes for muffins). They’re great slightly underbaked.