For the whipped cream:
Pour the heavy cream into a medium mixing bowl and put it in the freezer for 5 minutes (If you don't have room for the bowl, just put the heavy cream in the freezer.)
Take the mixing bowl of whipped cream out of the freezer and whisk with a large whisk until soft peaks form.

For the hot chocolate:
Bring milk to a boil in a medium sauce pot over medium-high heat.
Lower the heat to medium then add the chocolate, whisking vigorously until the chocolate is completely melted.
Add the milk powder and cornstarch, still whisking, until everything is dissolved and the mixture is smooth and thick.

To serve, divide the hot chocolate among four mugs or glasses, then garnish each with a large dollop of whipped cream.