Peel and finely dice the onions. Wash and coarsely grate the cucumber. Peel garlic and press it through a garlic press. Mix quark, yoghurt and milk, stir in half of the onions, garlic and cucumber and season with salt and pepper.
Mix lemon juice, 2-3 tablespoons of water, salt, pepper and sugar and add 1-2 tablespoons of oil. Clean, wash and slice the tomatoes. Clean and wash the lettuce, pluck into bite-sized pieces and drain.
Mix the tomatoes, olives, remaining onions and lettuce and pour the vinaigrette over it. Whisk the egg and cream in a deep dish. Mix breadcrumbs and paprika and also mix in a deep plate.
Cut the cheese slices in half, first turn in the egg, then in the breadcrumbs. Heat the remaining oil in a frying pan and fry the cheese slices in it until golden brown while turning. Arrange salad, fried cheese slices and a blob of tzatziki sprinkled with coarse pepper on plates.
Serve garnished with parsley and lemon slices. Serve the rest of the tzatziki extra. Flatbread tastes good with it.