Start boiling your water. I have a electric kettle that i fill up and it automatically stops when it boils.
Now fill your mug about half way full or the cream or milk. Add your hot chocolate mix. I use about 4 spoonfuls when i make it with cream and 3 spoonfuls with milk. I like my hot chocolate sweet. Mix your cream and mix together. When it is fully mixed, the cream should have little brown grainy things in it. If you taste it now, it should be just slightly too sweet. Put your mug in the microwave for about 45 seconds. I have a 1000 watt microwave so adjust accordingly. after it is done microwaving, mix it until it either is foaming on the top (cream) or had a whole bunch of bubbles (milk).