Place your coconut milk in the fridge overnight or in the freezer for 30 minutes to an hour. Upon removal, be careful NOT to shake the can as you want the cream to remain separated from the liquid.
Open the can and scoop the top layer of cream into a chilled mixing bowl. Whip on medium-high until soft peaks form. (Add a dash of the remaining coconut liquid if it's too thick.)
Add powdered sugar and vanilla and whip again to combine. Taste and adjust flavor/sweetness accordingly. Serve with hot cocoa and reserve the rest in an airtight container in the fridge for later use. Should keep for several days.