Place candy can in zip top bag and use a meat mallet or rolling pin to crush the candy and into small crumbs.
In a small pot, combine cocoa powder, sugar, and water. Heat over medium heat, whisking until a smooth chocolate syrup forms. Whisk in milk and add candy cane pieces. Heat, stirring often until milk is steaming and candy cane pieces have dissolved. Turn heat down if milk starts to simmer before candy is dissolved. Whisk vigorously to foam the milk slightly.
Pour coffee into an 8-ounce mug. Add milk mixture and heavy cream if desired. Taste and add more sugar if not sweet enough. Top with optional whipped cream, serve and enjoy!
Approximate nutritional information was calculated with 2% milk and no heavy cream or whipped cream.