Wash the potatoes, bring to the boil in a saucepan with water, cover and cook over medium heat for about 20 minutes. Then drain, rinse and peel. Cut the potatoes into slices.
In the meantime peel and finely dice the onion. Dab gherkins dry. Finely dice sausage and gherkins. Wash parsley, dab dry, garnish all but a few leaves, pluck them from the stalks and chop roughly.
Mix vinegar and parsley. Season with salt and pepper. Mix potatoes, cucumber, sausage, onion and vinaigrette and let it stand for a short time. Garnish with parsley.