Set your oven to 180°C (350°F). Grease and line a 9×5-inch loaf pan with parchment paper.

In a large mixing bowl, combine the melted butter, egg, egg yolk, sugar, yogurt, mashed bananas, and vanilla extract. Mix until smooth and well incorporated.

In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, stirring until just combined. Avoid overmixing to ensure a tender bread.

Warm the Nutella in a microwave-safe bowl for about 20 seconds to soften it. Gently fold the softened Nutella into the batter, creating a marbled effect. Do not fully mix; leave visible swirls.

Pour the batter into the prepared loaf pan, smoothing the top with a spatula. Place the pan in the preheated oven and bake for 50–60 minutes. Check for doneness by inserting a toothpick into the center; it should come out clean or with a few moist crumbs.

Allow the bread to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. Once cooled, slice and enjoy your moist, flavorful Banana and Nutella Bread.