Put the heavy cream in a bowl and add the sugar.
Put the cocoa powder through a tea strainer to sift and add (if you don't, you'll have lumps).
Immerse the bowl in ice water and mix slowly at first (if you mix on high, the cocoa powder will go flying about).
Once you've fully blended the cocoa powder, whip to your desired stiffness (whip until it's still slightly loose, and beat again just before use).
And here's a chocolate banana carp cake. Recipe ID: 1426948
Story Behind this Recipe
When making chocolate mousse from heavy cream, melting the chocolate can be a pain, so I used cocoa powder to make it easier.
When sifting the cocoa powder in and beating, be sure to put the bowl in ice water. With just heavy cream and sugar, it firms up quicker than usual when beating, so stop while it's still a bit soft! (If you find it to be too soft when you need to use it, just beat before use.) Use unsweetened cocoa!