Preheat your grill (or campfire coals) to a medium heat (around 350°F / 175°C).

Prepare the bananas: Leave the peel on. Slice lengthwise down the center, cutting through the peel but only about halfway into the banana flesh, creating a pocket. Do not slice all the way through the bottom end.

Stuff the bananas: Gently pry open the slit in each banana. Spoon Nutella evenly into the opening. Top the Nutella generously with miniature marshmallows and chocolate chips (if using).

Wrap the boats: Lay a large piece of heavy-duty aluminum foil flat. Place one stuffed banana in the center of the foil. Carefully wrap the foil around the banana, crimping the edges tightly to create a sealed pouch, ensuring the top remains slightly open to allow some steam to escape and the fillings to melt.

Grill: Place the foil-wrapped banana boats directly on the grill grates or near the hot coals. Cook for 10 to 15 minutes, turning occasionally (use tongs), until the banana peel is blackened and the filling is hot, gooey, and caramelized.

Serve immediately: Carefully remove the boats from the grill. Open the foil packets (watch for steam). Sprinkle with chopped nuts and dust with powdered sugar, if desired. Eat directly out of the peel with a spoon.