PREP: Preheat the oven to 350 degrees F. Line a 9x5 inch loaf pan with parchment paper OR generously spray with nonstick cooking spray and flour the interior. Don't skip prepping the pan or the bread likely won't come out very nice.
WET INGREDIENTS: In a small bowl, mash the bananas until well mashed and measure out 1 level cup. In a large bowl, combine the 1 cup mashed bananas with 4 tablespoons melted (and cooled to room temperature; don't add hot butter!!) butter, 2 tablespoons melted (and cooled) coconut oil, 2 large eggs, 3/4 cup yogurt, and 1/2 tablespoons vanilla extract. Mix with a wooden spoon until smooth and combined.
DRY INGREDIENTS: In a separate large bowl, combine the 2 cups flour, 3/4 cup white sugar, 1/4 cup brown sugar, 1 teaspoon baking soda, 1 teaspoon salt, and 1 cup chocolate chips. Whisk to combine. Add on top of wet ingredients and gently fold the dry ingredients into the wet until just combined. Do not over-mix.
BAKE: Pour half of the bread batter into the prepared loaf pan. In a microwave safe bowl, add the Nutella and microwave for 15 seconds. Drizzle all but 2 tablespoons Nutella on top of the batter. Smooth with the back of a spoon. Pour the rest of the bread batter on top of the Nutella. Add the remaining 2 tablespoons on top and use a knife to swirl the Nutella into the top half. Bake for 60 to 70 minutes, or until a toothpick when inserted in the center comes out clean or with few moist crumbs. Remove from the oven and let cool for 15 minutes into the bread pan before inverting to a cooling rack (do not rush this; it needs to time to set in the pan!) Once on the cooling rack, allow bread to cool for at least 30 minutes and preferably an hour before cutting in.
STORAGE: store any leftover bread in an airtight container at room temperature. Best eaten within 3 days.