Peel the cold jacket potatoes, cut thinly and place in a large bowl. Add onion slices, thinly sliced cucumber without a core, sliced radishes and chives.
Mix the mayonnaise and yogurt in a mixing bowl. Season to taste with mustard, vinegar, salt and pepper.
Then mix the whole thing into the salad, if necessary dilute with milk and season again with salt and pepper.
The potato salad should be prepared at least 2-3 hours before consumption, because it tastes better if it is well drawn.