1. Preheat the oven to 375˚F / 190˚C
2. Butter two Soufflé ramekins and sprinkle with cocoa powder, knocking out excess.
3. In a medium bowl, mix Nutella and two egg yolks.
4. In a separate medium bowl, whisk two egg whites until foam starts to form. Add sugar and continue mixing until they hold stiff peaks.
5. Fold 1/3 of the whites into the Nutella mixture until fully incorporated. Add the remaining whites to the mixture and fold gently, but thoroughly until the mixture is smooth.
6. Pour the mixture in the ramekins, clean the rims so the Soufflé rises evenly, and bake for 15 - 17 minutes.
7. Serve immediately.