Preheat your oven to 350°F. Grease and line a 9×5 inch loaf pan and set it aside.
In a large bowl, mix melted butter, oil, both granulated and brown sugars, and the bananas. Add the eggs and vanilla, and mix until just combined.
Add the flour, baking soda, and salt. Mix until all the dry ingredients are incorporated.
In a small bowl, combine melted chocolate and cocoa powder. Take about 1 cup of batter and place it in a medium-sized bowl. Mix in the chocolate until evenly combined.
Alternate scooping the plain banana batter and the chocolate batter into the prepared pan. Use a knife to swirl the two batters together. Top with chocolate chips.
Bake for 50-60 minutes or until it’s baked through. If the top is browning too quickly, create a tent with aluminum foil and gently place it over the top.
Allow the bread to cool completely before removing it from the pan. Enjoy your delicious and marbled chocolate banana bread!