Bring the lentils to the boil with 3/4 litres of water, cover and simmer over medium heat for 25-30 minutes. Wash the cutlets, dab dry and tap flatter. Spread the schnitzel thinly with tomato paste and mustard.
Cut the sausages into thirds, place 1 piece each on a cutlet and roll up. Fix with wooden skewers, put the rolls in a cool place. Clean and wash the soup greens. Cut leek and carrots into slices, dice celery.
Heat the fat in a saucepan and fry the soup vegetables vigorously. Add stock, bring to the boil and simmer covered for about 5 minutes. Add lentils, season with salt and pepper. Cover and simmer for another 5-10 minutes.
Heat the oil in a large frying pan and fry the escalope rolls vigorously on all sides. Season with salt and pepper, add 200 ml of hot water and braise covered for about 5 minutes. Wash parsley, shake dry and chop finely.
Stir the sauce thickener into the schnitzel braising stock and bring to the boil briefly. Season lentil vegetables with salt and pepper and arrange on a plate. Spread the cutlet rolls on the lentil vegetables and pour the stewed stock over them.
Serve sprinkled with parsley.