Boil the potatoes in water for about 20 minutes. Then drain, rinse with cold water, peel and leave to rest. In the meantime peel onions, halve them and cut into fine slices. Wash, clean, quarter and seed the tomatoes. Cut the flesh into small cubes. Clean and wash spring onions and cut them into rings, except for a piece for garnishing.
Clean salads, pluck off leaves, wash, dab dry. Cut romaine lettuce into fine strips. Cut frisée a little smaller. Peel garlic and ginger. Press garlic through a garlic press, dice ginger very finely. Cut potatoes into slices. Bring the stock to the boil briefly. Season with garlic, ginger, salt, pepper and sugar. Remove from the stove. Add vinegar and oil. Pour over the potatoes while they are still hot and let them steep for about 30 minutes.
Cut potatoes into slices. Bring the stock to the boil briefly. Season with garlic, ginger, salt, pepper and sugar. Remove from the stove. Add vinegar and oil. Pour over the potatoes while they are still hot and let them steep for about 30 minutes. Fold in remaining prepared ingredients. Garnish with olives and remaining spring onion