In a small pot, simmer cream, milk, sugar, salt and 1 1/2 cups of chopped chocolate truffles until sugar is dissolved, about 5 minutes. Remove pot from heat.
In a separate bowl, whisk yolks and vanilla extract. Whisking constantly, slowly whisk 1/3 of the hot cream into the yolks, then, whisk the yolk mixture back into the pot with the cream.
Return pot to medium-low heat and cook until mixture is thick enough to coat the back of a spoon. Pour into a large bowl, cover with plastic wrap and chill for at least 4 hours or overnight.
Churn chocolate truffle base in an ice cream machine according to manufacturer's directions.
Scoop churned ice cream into a large mixing bowl and add roasted hazelnuts and remaining chocolate truffle pieces. Use a wooden spoon or spatula to incorporate the nuts and truffles evenly into the ice cream base.
Serve Chocolate Truffle Ice Cream directly from the bowl as soft serve, or store in the freezer until ready to eat.