In a heat-proof bowl set over a pot of simmering water, add the chopped chocolate, heavy cream, and butter. Heat until melted and combined, stirring frequently. Remove from heat when most chocolate is melted but a few small chunks remain. Continue to stir off heat until smooth.

Stir in chocolate-hazelnut spread.

Chill in the fridge for 2-3 hours until firm and scoop-able. You can speed this process up by placing in the freezer for 30 minutes, then transferring to the fridge.

Use a tablespoon to scoop and portion chocolate, and roll in your hands to form a ball. Wipe hands clean in between every few truffles as needed.

Roll in crushed hazelnuts.

Store in the fridge until ready to serve. Truffles will keep for a week or more.