Here's my recipe:
Chocolate Avocado Mousse - 2-3 servings
1 ripe (soft) avocado
1 ripe banana
1 dollop Greek yogurt (1/4 cup if you're anal)
2 Tbsp quality cacao powder
2 Tbsp honey
Blend in food processor.
Comes out very thick and rich, because it's basically blended avocado, yogurt and banana, no need to wait for things or whip things.
edit: which I guess is not too dissimilar to this slightly more complicated recipe.