Warm heavy whipping cream in a saucepan and stir in hot chocolate mix, whisk until dissolved. 
Pour the hot chocolate into a cocktail shaker and add whiskey, chocolate syrup, and a few dashed chocolate bitters. Secure the lid and shake vigorously for 30 seconds. 
Divide the hot chocolate cocktail into serving glasses and top with your favorite whipped cream.
Garnish with chocolate shaving.
Serve.