Drizzle half of the chocolate syrup inside 4 chilled martini glasses, then add the remaining chocolate syrup to a shallow plate. Dip the top rim of each glass in the chocolate to coat them. Set aside.
Combine the vodka, chocolate liqueur, and irish cream in a cocktail shaker and add about a cup of ice to the shaker. Shake until thoroughly chilled and frosty on the outside of the shaker, 30 seconds to 1 minute.
Strain the cocktail into the prepared glasses. You can garnish with shaved chocolate if you’d like, then serve immediately.
Video
Notes
Can I garnish the glasses ahead of time? Yes! Decorate the martini glasses with the chocolate syrup, then store them in the fridge for a few hours. If your syrup is on the runny side, freeze the glasses instead to keep the syrup from running down the sides.
To make chocolate shavings: Run a vegetable peeler on the side of a chocolate bar. This will shave off thin, small shards of chocolate, perfect for garnishing the cocktail.