Peel the potatoes and celery. Cut celery, up to 1/3, and potatoes into pieces. Peel and chop onion. Heat 2 tablespoons of oil in a saucepan. Fry the potato and celery pieces and onion for 3 minutes.
Add stock, bring to the boil and cook over medium heat for 20 minutes. Knead the ground pork, egg and breadcrumbs. Season with salt and pepper. Form small dumplings from the minced meat. Heat 1 tablespoon of oil in a frying pan and fry the dumplings for 8 minutes over medium heat until they are round.
Mash the potatoes and celery in the broth. Season to taste with salt, pepper and lemon juice. Add cream. Warm the meatballs in the soup. Cut remaining celery into thin strips. Heat 1 tablespoon of oil in a pan.
Fry the celery strips and sugar for 3 minutes until golden brown. Wash the chives, dab dry and cut into rings. Fill potato-celery soup into plates, spread celery strips and sour cream on top and serve sprinkled with chives.
Roasted rye bread tastes good with it.