In a medium saucepan set over medium heat, add 1 cup of the cream, the milk, sugar and salt, and bring to a simmer.
Rub the hazelnuts with a dishtowel to remove as much of the skin as possible. Place the hazelnuts in the bowl of a food processor and pulse until finely chopped. Add the hazelnuts to the milk mixture, then remove the saucepan from the heat and cover for 2 hours.
Add the chocolate to a mixing bowl and set aside. Bring the remaining 1 cup cream to a boil and pour over the chocolate. Stir until silky smooth.
Pour the hazelnut mixture through a fine mesh sieve into a saucepan and discard the hazelnuts. In a separate bowl, whisk the egg yolks. Pour the warm hazelnut mixture slowly into the yolks while stirring constantly. Transfer the hazelnut mixture back to the saucepan and reheat on the stovetop, then pour through a fine mesh sieve into the chocolate mixture. Add the vanilla and cool over an ice bath, then refrigerate for 3 hours. Process the ice cream base in an ice cream maker according to the manufacturer's instructions. Transfer the ice cream to a serving container and freeze until firm, about 2 hours. Serve cold.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.