In a saucepan, melt the butter and milk powder over medium-low heat. Whisk continuously until the butter and milk powder are combined.
8 Tablespoons (1 stick or 113 g) unsalted butter, 2 Tablespoons (18 g) nonfat milk powder
Bring butter to a boil. The mixture should be rapidly bubbling.
Whisk continuously until the butter begins to brown. There should be small brown bits on the bottom and sides of the pan. Remove from the heat immediately to cool to room temperature. Put it in the refrigerator if needed. See photos above.
While the butter cools, whisk together the flour, cinnamon, baking soda, and salt. Set aside. Prepare a 9 x 5 inch loaf pan with parchment paper. Preheat the oven to 350 degrees.
2 cups (260 g) all-purpose flour, 1 1/2 teaspoons ground cinnamon, 1 teaspoon baking soda, 1/2 teaspoon salt
Once the butter is at room temperature, in a large bowl, whisk together the brown butter, brown sugar, and granulated sugar.
1/2 cup (100 g) brown sugar, 1/2 cup (100 g) granulated sugar
Add the bananas and yogurt. Whisk until well combined.
1 3/4 cups (403 g) mashed bananas, about 4 medium bananas*, 1/2 cup (120 g) Greek yogurt, room temperature*
Add the egg and vanilla. Whisk until combined.
2 large eggs, room temperature, 2 teaspoons vanilla extract
Add the flour mixture and the chocolate chips. Fold until just combined.
3/4 cup semi-sweet chocolate chips, plus more for topping*
Transfer the batter into the prepared pan. Sprinkle more chocolate chips on the top if desired.
Bake for 65-75 minutes, covering loosely with foil after about 30-35 minutes or when the bread is brown. It is ready when a toothpick inserted in the center comes out mostly clean with a few moist crumbs. It continues to cook as it cools. Allow the bread to cool in the pan on a wire rack for 1 hour. Remove from the pan and continue cooling the loaf on the rack.