Using a hand mixer, whip the heavy cream and sugar until stiff peaks form. In a medium saucepan, warm the milk over medium heat until nearly simmering. Don’t let it come to a boil. Add the chocolate and whisk until fully incorporated and the mixture starts to thicken a little bit. In a heat-proof glass mug, pour in a layer of hot chocolate. Pour a shot of espresso over the back of a spoon over the hot chocolate to form the second layer. Gently top with whipped cream for the third layer and serve.