Chocolate Banana Marble Bread

Ingredients:
3 medium very ripe bananas, at room temperature
1/4 cup buttermilk, at room temperature
2 teaspoon vanilla extract
2 cups sifted cake flour
1 teaspoon baking soda
3/4 teaspoon baking powder
1/4 cup unsifted unsweetened good cocoa powder
3 tablespoon boiling water, plus more if needed
180gm unsalted butter, softened
1 cup sugar
2 large eggs, at room temperature, lightly beaten

Instructions:

1. Preheat oven to 175C. Lightly spray the 9 x 5 inch loaf pan with vegetable oil and line with a parchment paper that extends 1 inch beyond the long edge of both side s of the pan.
2. Peel the bananas and mash them with a fork or using a food processor. Mash or process to a smooth puree. Measure 1 cup of the puree and transfer it to a medium bowl. Add the buttermilk and vanilla and whisk until blended. Set aside.
3. Sift the cake flour, baking soda and baking powder into a medium bowl. Whisk to blend well and set aside.
4. Place the cocoa powder in the small bowl. Pour the boiling water over the cocoa powder and stir until smooth. If it is too thick, add a little water. Set aside.
5. Combine the butter and sugar in the bowl of a stand mixer. Beat on medium high until the butter is very light and white in colour, about 4-5 minutes. Scrape down the bowl with a silicone spatula.
6. On medium speed, gradually add the beaten eggs, 1 tablespoon at a time. About halfway through, turn the mixer off and scrape down the bowl. Continue adding the rest of the eggs. Scrape the bowl again.
7. On low speed, add one third of the flour mixture. Add half of the banana mixture. Repeat with the flour-banana-flour. Scrape down the bowl and finish blending the batter by hand using a silicone spatula.
8. Transfer half of the batter to a clean medium bowl. Add the cocoa paste and blend well.
9. Drop alternating spoonfuls of dark and light batters into the prepared pan, then marbleize by using a spoon or knife.
10. Bake the cake for 55-60 minutes or until a cake tester inserted into the center of the cake comes out clean.
11. Transfer the cake to a wire rack and let it cool completely in the pan. When cool, remove from the pan, peel off the parchment paper and cut slices with a serrated knife.

Note:

To ensure that the cake has an intense burst of banana flavor, be sure to use bananas that are very ripe and soft, with plenty of black spots speckling their skins.