Place a sheet of parchment paper over a flat tray that will fit in your freezer.

In a medium microwave-safe bowl, melt butter in the microwave. Add Nutella and stir until butter is completely incorporated.

Using a baking spatula, spread mixture over about a 5 by 10-inch rectangle on the tray, so it is approximately 1/4-inch thick all over.

Place in the freezer for at least an hour.

Once frozen, transfer the block, still on the parchment paper, to a cutting board. Use a large chef's knife to chop the block into small chunks. You want to do this process fairly quickly as the mixture will melt easily in a warm kitchen and from the heat of your hands. If your kitchen is warm, and your chips have begun to stick to each other, slide the paper back onto your tray and pop everything into the freezer for 15 minute or so to firm back up. Once solid, gently break up any stuck-together pieces and continue.

Lift the parchment paper and pour chips into an air-tight container and immediately place back in the freezer. Keep in the freezer until just before adding to your dessert. Use within two weeks.