Simple to make but beautiful to serve, this marbled bread isn’t your usual banana bread made from overripe bananas. The layering of batters makes sure that each slice gets a healthy helping of chocolate and the use of Kahlúa throughout the batter gives an adult coffee flavored twist in this loaf. I try to use bananas that walk the edge between ripe (a day or two past freckled brown) and over ripe (completely black), but whatever bananas you use will work as I cook them first to help concentrate the banana flavor. You’ll note that I use bread flour in the batter, which gives a nice chew to the final product but if you don’t have any, feel free to substitute in the same amount of all-purpose flour, just keep in mind the banana bread will come out slightly softer and more cake-like.
Preheat the oven to 350˚F and spray a standard 9 x 5 inch bread loaf pan with cooking oil. Set aside and make the banana mix-in by peeling and slicing the ripe bananas into 1-inch disks in a bowl with the dark brown sugar and cinnamon. Toss to coat. Place the butter in a large skillet pan and turn the heat to medium high. Once the butter has melted and starts to sizzle add the bananas with the sugar and cinnamon, scraping any liquid that may have developed. Stir with a wooden spoon, breaking up the banana as it cooks. As the bananas start to fall apart, the juices will start to thicken (2-5 minutes depending on how ripe the bananas are). Add the Kahlua and the vanilla and continue to cook until the bananas have mostly fallen apart and the mix-in looks thick and dark brown. Set aside to cool slightly.
Make the bread batter by placing the flours, salt, baking soda, baking powder in a large bowl. Stir vigorously with a balloon whisk until uniform in color and the dry ingredients are evenly distributed. Place the sugar and melted butter in the bowl of a stand mixer fitted with the paddle attachment. Beat until the sugar has start to dissolve a bit, about 30 seconds. Add half the dry ingredients and beat until incorporated. Add the warm bananas mix-in from the skillet and beat until incorporated. Repeat with the remaining dry ingredients and then end with the Greek-style yogurt.
Scoop out about a 1/3 of the batter into the bowl that had the dry ingredients. In a liquid glass measuring cup, measure out the Kahlúa and then add the cocoa powder to it. Stir together to form a thickened paste. Scrape into the smaller batter and stir together.
Spoon the batter into the prepared bread loaf pan, alternating different batters, some of the regular banana bread batter, some of the Kahlúa chocolate batter on top of each other. Once you’ve finished spooning all the batter into the pan, take a butter knife and make one or two “figure-eight” swirls in the pan, to help marble the batter together. Don’t over-stir though, you want the batter to marble not mix. Bake in the oven for 55-60 minutes or until a toothpick inserted in the middle comes out clean. Cool in the pan for 15 minutes before turning out the warm loaf onto a wire rack to cool completely.