In a double boiler over barely simmering water, combine chocolate, butter, heavy cream and Nutella. Heat until chocolate is melted. Stir until you have a smooth mixture.

Remove from chocolate mixture from heat and allow it sit at room temperature for about 10 minutes.

Whisk in vanilla and Frangelico.

Pour mixture into a shallow dish (example: 8x8 pyrex dish) and cover with plastic wrap. Refrigerate for about 2 hours. If you refrigerate longer than two hours, the mixture will be too hard to work with. If this occurs, allow the mixture to sit at room temperature until they are pliable enough to work with.

Line a baking sheet with parchment paper.

Using a small scoop (2 teaspoons) or a melon baller, scoop out chocolate mixture, roll into one inch balls, and place on prepared baking sheet. Continue with remaining chocolate mixture.

Roll balls in chopped hazelnuts.

Refrigerate truffles until ready to serve.