Add whiskey, vodka, chocolate liqueur, and half of the milk to a cocktail shaker with ice. Shake for about 5 seconds to chill, then strain into a martini glass.
If you have a milk frother, use this to froth up the remaining milk, then pour on top of the martini. If you don't have a milk frother, you can simply add all of the milk to the cocktail shaker and skip this step.
If desired, top with whipped cream and cookie crumbs.
Notes
Recipe intended for readers 21+Nutrition information is an estimate only.