Wash the potatoes thoroughly and cook in plenty of boiling water for 20-25 minutes. Rinse potatoes under cold water, drain and peel. Quarter potatoes lengthwise and let them cool down a little. Meanwhile peel and finely dice the onion. Chop olives finely, except for 3 pieces.
Wash basil and chives, dab dry and chop finely, except for a little for garnishing. Mix vinegar, salt and pepper. Add the oil at the end. Stir in chopped olives, herbs and onion. Mix the marinade with the potatoes and let it stand for about 20 minutes. Drain the mozzarella balls. Wash the tomatoes, drain and cut in half. Fold the mozzarella balls and tomato halves into the potato salad. Season salad with salt and pepper and arrange on a plate.
Mix the marinade with the potatoes and let it stand for about 20 minutes. Drain the mozzarella balls. Wash the tomatoes, drain and cut in half. Fold the mozzarella balls and tomato halves into the potato salad. Season salad with salt and pepper and arrange on a plate. Serve garnished with basil and remaining olives