1. Place Nutella in microwave safe bowl. Microwave for a few seconds until soften. Let cool.
2. beat the heavy cream until it forms stiff peaks. Gently fold in the melted Nutella until no streaks remain.
3. Transfer the mousse to a piping bag. If the mousse too runny, refrigerate for 1 hour in the piping bag. Pipe into serving dishes and refrigerate for at least 4 hours.
4. Top with chocolate and nuts.