Peel and finely chop the onion. Peel and wash the potatoes. Cut blue potatoes into pieces. Heat oil in a pot. Sauté potato cubes and onion in it. Add stock, bring to the boil, cover and cook for about 20 minutes
Slice the remaining potatoes into thin slices. Heat the frying fat. Fry the potato slices for 2-3 minutes in portions until brown. Remove the potato chips, let them drip off on kitchen paper, season with salt and paprika
Finely puree the soup, season to taste with salt, pepper, vinegar and sugar. Wash the dill, shake dry. Pluck flags from the stems and chop finely. Arrange soup in bowls with some potato chips, sprinkle with dill