Add the sugar-free chocolate pudding mix and cold milk to a large bowl. Whisk vigorously for about 1–2 minutes, until thickened.
Whisk in the chocolate protein powder, Greek yogurt, vanilla, cocoa powder, and a tiny pinch of salt until completely smooth.
Add the sugar-free Cool Whip and gently fold it into the chocolate mixture using a spatula. Avoid vigorous stirring so the fluff stays light and airy.
Divide into 4–6 serving cups. Cover and refrigerate for at least 1 hour.
Add a small spoonful of sugar-free Cool Whip or a light dusting of unsweetened cocoa before serving.
