Peel and dice the onion. Heat the oil in a saucepan and sauté the onion in it.
Wash, drain and add brown lentils. Pour 1.5 liters of water and bring to the boil. Season with broth and thyme. Cover and simmer for approx. 1 hour.
Clean and wash the soup greens, cut the carrots and leek into slices or rings. Dice the celery. Peel and quarter the potatoes and after approx. 45 minutes add them to the lentils with the soup greens.
Add red lentils in the last 10 minutes and cook at the same time.
Stir the sour cream into the stew and season with salt, pepper and mustard. Wash, dry, chop the parsley and pour over the stew.
Can also be frozen well, but only add the sour cream after thawing.