Make Brown Butter Baked Churro Donuts according to recipe.
Heat your panini maker/sandwich press. Meanwhile, carefully slice donuts in half lengthwise with a serrated knife. Slather on a thin layer of nutella on one half, and marshmallow fluff on the other. Place the halves together and cook on your panini press/sandwich maker for approximately 1 minute, until the sugar on the donut caramelizes a bit and the filling gets all ooey-gooey (yes, that’s a technical cooking term). Let cool slightly, then devour.