Place a large glass or metal mixing bowl and whisk attachments in the freezer for 10 minutes to chill.

Pour the chilled heavy whipping cream into the cold bowl.

Sift the cocoa powder and powdered sweetener over the cream to ensure a smooth, lump-free texture.

Whip on low speed for 30 seconds to incorporate the dry ingredients, then increase to high speed.

Continue whipping for 2 to 3 minutes until stiff peaks form and the mixture holds its shape.

Spoon the mousse into four ramekins and serve immediately, or refrigerate for 1 hour for a firmer consistency.