1. Whip cream to soft peaks stage.
2. Make zabaglione in a double boiler. Add egg yolks, sugar and liqueur into bowl and whisk continuously for mixture to thicken. (takes approx 5-10 minutes)
Once ready the zabaglione should leave a trail when the whisk is lifted out.
3. Add in finely chopped chocolate and Nutella to the zabaglione, and stir through until melted. If the mixture seizes, then add 1/4 cup water and stir until combined. It will bring it back together.
4. Whip egg whites until foamy, add in sugar and whip until firm peaks hold.
5. Add cream to chocolate zabaglione and fold through.
6. Add egg whites to the mixture and fold through. Then pour into a loaf pan lined with plastic wrap. Level off, cover with plastic wrap and freeze for 6 hours min.
7. Once frozen, turn out onto a serving platter and remove the plastic wrap. Decorate with warmed Nutella and toasted hazelnuts.