In a saucepan, whisk together heavy cream, marshmallow cream, 1/3 hazelnut spread, and milk. Heat over low heat until blended and heated.
To serve, place one Tbsp of remaining hazelnut spread into the bottom of each of 4 clear glass mugs. Ladle in the hot chocolate carefully (do not stir) over nutella, then top with a large dollop of marshmallow whipped cream (recipe below). Garnish chocolate shavings.