Rinse and dry the greens well.
Chop the ribs, peel the onion.
Fold in a saucepan and cover with cold water, put on fire. Skim off the foam and remove the onion, cook for about an hour.
Rinse greens, dry and chop finely.
Add diced potatoes to the broth and cook for 5-7 minutes over medium heat.
Add greens, stir and salt. Cover and let it brew for 10-15 minutes.
Serve with sour cream.