Cut the onion into half rings and marinate for 15 minutes. For the marinade: pour vinegar into the marinating container, add sugar. Pour boiling water, stir and put the onion. Meanwhile, remove the skin from the eggplant and cut the eggplant into not very long strips.
In a preheated frying pan, pour the olein oil and fry the eggplants until tender.
Put the finished eggplants on paper towels and let them cool. In a salad bowl, put the pickled onion, after squeezing it out of excess liquid. Cut the eggs into small cubes, add the eggplant. Season the salad with mayonnaise and mustard, add a pinch of salt. Mix the salad.