4 tablespoons unsalted butter, melted and cooled slightly
2 tablespoons plain Greek yogurt (I use nonfat)
¼ cup buttermilk (or sour cream)
1 large egg
1 teaspoon vanilla extract
1½ cups all-purpose flour
1 tablespoon espresso powder
1 tablespoon ground flax seed
1½ teaspoons baking soda
1 teaspoon salt
1 cup semisweet chocolate chips
Preheat oven to 350°F. Butter and flour one loaf pan and set aside.
In a large bowl, mix together the mashed bananas, sugars, butter, yogurt, buttermilk, egg, and vanilla. In another bowl, whisk together the flour, espresso powder, ground flax, baking soda, and salt. Toss 2/3 cup of the chocolate chips in the flour mixture (reserve the other 1/3 for the top of the banana bread). Pour the dry ingredients into the wet and stir until just combined.
Pour into prepared loaf pan. smooth out the top, and then top with the remaining chocolate chips.
Bake for 50-60 minutes, or until the top is golden and a toothpick inserted in the middle comes out clean (baking time will vary by oven). Let cool in the pan for 15 minutes and then invert onto a wire rack to cool completely.
Slice and eat (one piece at a time, if you can manage it!).