Soak the bread cubes in the milk for 2-3 minutes. Add the tartare, red onion, mustard, tomato paste, salt, pepper, red chilli pepper, and garlic. Knead thoroughly until well combined. Let rest for 3-5 minutes, then season to taste.
Divide the camembert (or Gouda or mozzarella) into 8 oblong flat pieces. Shape the meat mixture into 8 meatballs, pressing a cheese piece into the center of each.
Heat the clarified butter in a large pan over medium heat. Add the meatballs and fry for 10 minutes. Turn and fry for another 10 minutes, turning occasionally, until the internal temperature reaches 75°C (160°F).