Wash the potatoes, put them in a saucepan of cold water with their skins on, cover, bring to a boil, and cook at a steady but moderate boil until they are tender enough to be easily pierced by a fork. Drain.
Peel the potatoes while they are hot and cut them right away into ¼-inch slices. Try to keep the slices whole, if possible, using a fine, sharp knife, but do not worry if they break apart—it won’t affect the taste.
Put the sliced potatoes in a warm ceramic or glass serving bowl, sprinkle salt on liberally, drizzle immediately with vinegar, and toss gently. They should still be quite warm when you add the vinegar. Add the olive oil, onion, black pepper, chopped pickles, and parsley; turn the potatoes over several times; let them steep in their seasonings until they come to room temperature; then serve.