Prep your pan and oven. Heat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with a parchment sling so you can lift the bread out easily.

Warm the Nutella. In a small bowl, stir the Nutella with a splash of warm milk until it’s smooth and pourable, like thick hot fudge. This makes swirling easier and prevents heavy clumps.

Mash the bananas. In a large bowl, mash the bananas until mostly smooth with a few small lumps. You want texture, not baby food.

Mix the wet ingredients. Whisk in the granulated sugar, brown sugar, oil (or melted butter), eggs, and vanilla. Stir until the mixture looks glossy and combined.

Combine the dry ingredients. In a separate bowl, whisk the flour, baking soda, baking powder, salt, and cinnamon (if using).

Bring it together. Add the dry mixture to the wet mixture and fold gently just until no streaks of flour remain. If you’re adding nuts or chocolate chips, fold them in now. Do not overmix.

Layer and swirl. Pour half the batter into the prepared pan. Dollop half the warm Nutella over the batter in spoonfuls. Add the remaining batter on top, then the remaining Nutella. Use a butter knife to make a few gentle figure-eights through the loaf. Stop before it looks uniform—you want distinct swirls.

Bake. Place the pan on the center rack and bake for 55–70 minutes, depending on your oven. Start checking at 55 minutes. The loaf is done when a tester inserted in the center comes out with a few moist crumbs (avoid testing directly through a Nutella pocket, which will stay gooey).

Cool properly. Let the bread cool in the pan for 15 minutes, then lift it out to a wire rack. Cool at least another 45–60 minutes before slicing so the crumb sets and the swirls don’t smear.

Serve. Slice with a serrated knife for neat edges. Enjoy as is, or warm a slice for 10–15 seconds and top with a pat of butter or a sprinkle of flaky salt.