Boiled red potatoes, hard-cooked eggs, red onion,and parsley are dressed in muscatel-wine vinegarand olive oil.
Prepare an ice-water bath; set aside. Cover eggs with water in a medium saucepan; bring to a full boil. After 1 minute, cover; turn off heat. Let stand 8 minutes. Rinse; transfer to ice-water bath.
Cover the potatoes with water by 1 inch in a large saucepan. Bring to a boil; add salt. Simmer until just tender, about 15 minutes (do not overcook). Drain potatoes; let cool slightly. Halve lengthwise.
Transfer potatoes to a medium bowl. Add vinegar to taste; gently toss. Stir in parsley and onion. Gently tossing, pour in oil in a slow, steady stream; toss until incorporated. Season with salt and pepper.
Just before serving, peel and quarter eggs, and arrange on top of salad.