Wash the potatoes and cook in boiling water for about 20 minutes. Clean, wash and cut the salad into bite-sized pieces. Wash tomatoes, dab dry and cut in half. Mix mayonnaise, mustard, oil and vinegar. Season with salt and pepper. Wash chives, dab dry and cut into small rolls.
Add to the salad dressing. Drain potatoes, rinse with cold water and peel. Let cool and cut into slices. Mix potatoes, salad, tomatoes and dressing. Arrange on a plate