Wash the chicken filet, dab dry and cut in half crosswise. Wash the leek, remove 2 leaves. Blanch the leek leaves for about 1 minute in boiling water, drain. Wrap the leek leaves around the medallions and pin them with wooden skewers. Cut remaining leek into rings. Put rice in plenty of boiling salted water and cook for about 20 minutes.
Heat oil in a pan. Fry the chicken medallions for about 12 minutes. Season with salt and pepper. Cut Mozzarella into 2 slices. Put cheese on the meat and sprinkle with some marjoram. Cover and fry on low heat for another 4 minutes
Put the leek rings and 1 tablespoon of water in a pot and steam the leek for about 1 minute. Add tomato pieces and tomato paste, bring to the boil. Let simmer for about 2 minutes. Season with salt, pepper and marjoram. Drain the rice and let it drain. Arrange chicken medallions, tomato sauce and rice on plates. Garnish with parsley