Light a side burner of the barbecue. Place the hazelnuts in a saucepan and toast on side burner over medium heat for 4 minutes, or until toasted. Pour hazelnuts into a tea towel, rub tea towel to remove the skins from the hazelnuts. Set aside.
Return the saucepan to the side burner and add the milk. Heat milk over high heat, until the milk is warm and beginning to steam. Reduce the side burner to medium, add the Nutella, cocoa powder and sugar. Wisk until hazelnut and sugar is dissolved and the hot chocolate has come to a gentle boil. Take off the heat and pour into mugs. Top with marshmallows, chocolate bits and hazelnuts