Place mixing bowl and beaters in freezer 30 minutes before beginning to mix.

Place heavy whipping cream in the chilled bowl and begin to whip with electric mixer. Whip until cream begins to thicken and looks a little frothy.

Sift cocoa and powdered sugar into the bowl. Give the cream a stir with a spoon or spatula to moisten the powders. Then whip the cream again until stiff peaks form.

Spoon or pipe mousse into serving glasses and refrigerate til ready to serve.