In a blender or food processor, combine the cottage cheese, cocoa powder, sweetener, and vanilla extract.
Blend on high until completely smooth. If the mixture looks grainy, continue blending until creamy.
Spoon the mousse into serving dishes.
Chill for 20–30 minutes for a thicker consistency, or enjoy immediately for a fluffier texture.
Garnish with your favorite toppings such as whipped cream, fresh fruit, or chocolate shavings.