Wash the potatoes and cook in boiling water for about 15 minutes. Stir honey, mustard and vinegar until smooth. Season with salt and pepper. Gradually add the oil. Drain potatoes, rinse, peel and halve. Pour the honey-mustard marinade over them and let them stand for about 15 minutes.
Season. Wash the watercress and pluck the roots. Drain the cress. Wash, clean and halve the tomatoes. Mix olives, tomatoes and watercress with the potatoes. Season and arrange again if necessary.