In a small saucepan, warm the heavy cream over medium heat until it begins to steam but not boil.
Add the chocolates
Remove from heat.
Stir in: milk chocolate, dark chocolate, nutella until completely melted and smooth.
Add the cocoa, butter, and flavorings
Return to low heat. Add: cocoa powder, butter, vanilla, salt, rangelico (if using)
Whisk until silky and fully blended.
Stir in the finely chopped toasted hazelnuts.
Adjust consistency, If you want it: Thicker, simmer 2–3 minutes. Thinner, add 1–3 tablespoons warm cream.