Boil the chestnuts and peel them.
Mash the boiled chestnuts and mix them with Greek yogurt.
Prepare espresso.
Mix low-calorie sweetener with the espresso.
Put the chestnut-yogurt mixture in a glass cup and pour the espresso over it.
Sprinkle cocoa powder on top.
Chill in the refrigerator for about 1 hour before eating.