First, heat the milk. If you’re using the microwave, heat at 20-30 second intervals, then stir and test. If you're heating on the stove, be sure to not let the milk overheat or boil. Whip the milk using a whisk, a frother, or a hand mixer until the surface is nice and foamy.
Add your flavoring syrup to your cup. If you're using hard chocolate, heat the chocolate together with the milk in a double boiler over medium-low heat, stirring until combined. Then pour it into the cup.
Pour in the espresso and milk, and whisk all of the ingredients together.
Top your mocha with whipped cream.