Make the custard. In a medium bowl whisk together the milk, heavy cream, egg, and vanilla. Set aside.

Remove crusts from bread slices and flatten with a rolling pin.

Spread Nutella on each bread slice and roll up, pinching the seam to secure.

Heat 2 tablespoons of butter in a skillet over medium heat. Dip rollups in custard, then cook until golden, about 2 minutes per side.

Once cooked, roll the rollups in vanilla sugar or dust with powdered sugar. Serve immediately.