In a small saucepan, bring the cream to a boil. Add the gianduja chocolate and vanilla. Remove from heat, and stir until melted. Stir in the hazelnuts until incorporated. Transfer to a medium bowl. Stir in the butter. Refrigerate until firm, about 30 minutes.Advertisement
When ready to use, remove from refrigerator and stir with a wooden spoon until softened, about 1 minute.