Clean the mushrooms, wash them briefly if necessary. Peel onion and garlic. Cut onion into strips. Dice garlic finely.
Heat the oil in a large pot. Fry the gyros, onion and garlic thoroughly. Fry the mushrooms briefly. Add tomatoes and juice, 1⁄8 l water and chili sauce and bring to the boil. Season with oregano, salt and pepper.
Cover and simmer for about 10 minutes.
Feta crumble. Warm the olives briefly in the soup. Serve the soup, spread the feta on top. Flatbread tastes good with it.