Cut the rind off the bacon. Rinse lentils in a sieve with cold water and drain. Put the lentils, bacon, bay leaf and marjoram in a large pot. Add approx. 1 1⁄2 l water, bring to the boil, cover and simmer for approx. 45 minutes.
Soup greens, carrots and potatoes clean or peel, wash and cut into small pieces. Add vegetables and potatoes to the lentils and cook for another 30 minutes.
Remove the bacon about 15 minutes before the end of the cooking time and cut into strips. Cut mettenden into thick slices. Add both to the soup and simmer for about 5 minutes. Season stew with salt, pepper, vinegar, mustard and 1 pinch of sugar.
Arrange the lens pot.