Preheat oven to 350 degrees F. Arrange the hazelnuts in a single layer on a rimmed baking sheet. Bake in preheated oven until golden brown and fragrant, 13-15 minutes.
In a food processor, blend the roasted hazelnuts and sugar until it becomes a smooth paste.
Chop the chocolate into small pieces. Melt until smooth using either the microwave in 20 second increments or in a heatproof bowl over a pot of simmering water.
Transfer the melted chocolate to the bowl of a stand mixer fitted with a whisk attachment or a large bowl. Whisk in the butter, then the cream, salt, and smooth hazelnuts until blended.
Pour into containers, preferably glass, and allow to cool. Cover and refrigerate for up to 4 weeks.