If you are looking for something chocolate and easy to make, try this mousse from Michael Simon.
1 c. heavy cream, very cold
1/2 to 1 t. instant espresso powder, your preference, I use 1 t. (omit for kids)
1/2 c. Nutella
Optional: Sliced bananas
Combine cream, espresso powder, and Nutella in a mixing bowl
With the whisk attachment, beat on medium speed for 1 minute
Scrape sides and bottom and continue beating until medium peaks form
Transfer to a smaller bowl and freeze at least a half hour
If you freeze the mousse completely, let it stand on the counter 10 minutes before serving
Garnish with sliced bananas, if desired