In a bowl, combine minced beef, chopped onion, pressed garlic, mustard, egg, dried parsley, vegetable stock, and quark. Season with salt and pepper to taste. Shape mixture into small patties.
Heat roughly 2 tablespoons of vegetable oil in a pan over medium heat. Pan-fry patties for 15-20 minutes, turning occasionally, until cooked through (internal temperature 71°C / 160°F).
Alternatively, bake patties in oven at 200°C (392°F) conventional or 180°C (356°F) fan-assisted for 20-25 minutes until cooked through (internal temperature 71°C / 160°F).