Chop the chocolate into small pieces so that it will melt quickly in the hot cream (you can also use chocolate chips instead of chopped chocolate); place it in a medium bowl.
Put the heavy cream in a saucepan over medium heat and bring to a simmer. Alternatively, you can heat it in the microwave until it starts to bubble (it should be hot but not boiling)
Pour the hot cream over the bowl of chocolate and let it sit for a few minutes - depending on how hot your milk is, you might want to wait up to 5 minutes (waiting allows the hot cream to melt the chocolate but also brings down the temperature of the cream...if you mix it while the cream is too hot could cause the ganache to break, resulting in some grittiness).
Once you have waited a bit, put your whisk in the middle of the bowl and whisk in a small circle slowly moving outward, slowly making bigger circles (this ensures that you are slowly incorporating the cream into the chocolate, creating an emulsion and ensures a silky smooth ganache).
