Soak the stale bread roll in water or milk for 2-3 minutes. Season the minced meat with the spice mixture. Squeeze out the soaked bread well by hand and add to the minced meat with the whole egg. Knead everything together until uniform. Shape into small dumplings using moistened hands. Dice the onions, carrots, and celery as listed in the ingredients.
Preheat your oven to 175°C (350°F). Heat the clarified butter in a Dutch Oven or oven-safe pot over medium-high heat. Working in batches if necessary, fry the meatballs for 5-8 minutes per batch until golden brown on all sides. Transfer to a plate.
In the same pot over medium heat, cook the diced vegetables for 5 minutes, stirring occasionally. Return the meatballs to the pot.
Pour the tomato sauce over the meatballs and vegetables. Sprinkle with grated lemon peel. Cover with the lid and transfer to the preheated oven. Braise for 30 minutes.
Remove the pot from the oven, stir in the oregano, cover again, and braise for 15 more minutes.
If desired, stir in the whipped cream or crème fraîche. If the sauce is too thick, thin it with a little water.