Well I just made this up and it is delicious -the most wonderful quick chocolate craving satisfier.

Take 1/2 cup of plain yoghurt and 1/2 cup of cream. whip the cream until quite thick. ( We only have one type of whipping cream in New Zealand and I think it equates to heavy cream in the US). Add 1/2 tablespoon cocoa powder -unsweetened, add some artificial sweetner. Mix it up. Eat it.

According to my Lifeform software it has 6 grams of carbs.
(I deducted 4 grams of carbs from the yoghurt as the yoghurt culture eats 8 grams for each cup). So the yoghurt = 1 gram, the cream 4 grams and the cocoa powder 1 gram. Adjust carbs for the brands you have available.