1 1/2 cups chilled heavy whipping cream, divided
1/2 cup plus 1/3 cup marshmallow cream (fluff), divided
1/3 cup plus 4 heaping tablespoons hazelnut spread (Nutella), divided
3 1/2 cups whole milk
Chocolate sprinkles or chocolate shavings for garnish
Beat 1 cup heavy cream and 1/2 cup marshmallow cream in the bowl of an electric mixer on high speed with the whip attachment until medium peaks form. Refrigerate until needed.
In a medium heavy bottom saucepan, whisk together 1/3 cup hazelnut spread, remaining 1/3 cup marshmallow cream, 3 1/2 cups milk, and remaining 1/2 cup heavy cream over low heat until smooth and hot.
To serve, place one heaping tablespoon of hazelnut spread into the bottom of each of 4 clear glass mugs. Ladle in the hot chocolate carefully (do not stir) over spread, then top with a large dollop of the whipped cream. Garnish with sprinkles or chocolate shavings and serve with extra whipped cream.