Peel and dice the sweet potatoes and cook in salted water for about 8 minutes. Drain over a sieve and rinse with cold water so that they do not continue to cook. Dice the mozzarella and set aside.
Preheat the oven to 200 degrees top / bottom heat.
Peel the onion and garlic, chop them into small cubes and sauté with the butter in a pan until translucent. Season with pepper and stir in all the herbs and cream. Turn off the heat.
Fold in the sweet potato and mozzarella cubes, season to taste and pour the mixture into a small baking dish. Baked in the oven for 10 minutes, the cooking time may vary.
The potatoes are eaten hot straight out of the mold.