Peel, wash and quarter the potatoes. Cook in boiling salted water for 15-20 minutes. Peel onion and chop coarsely. Clean, wash and slice the zucchini and eggplants.
Heat 2 tablespoons of oil in a frying pan. Sauté the onions in it until transparent. Add zucchini, braise for 4-5 minutes and season with salt and pepper. Remove from the pan. Mix 40 g flour and some salt and turn the eggplant slices in it.
Heat the rest of the oil in a frying pan and fry the aubergines in it in portions until golden brown. Drain on kitchen paper. Wash the cherry tomatoes, drain and cut in half depending on size. Cut the turkey breast into cubes.
Drain the potatoes, mix them with the rest of the vegetables and put them into a greased casserole dish. Heat the fat in a saucepan and sauté the remaining flour in it. Add stock and milk while stirring, bring to the boil and simmer for about 5 minutes.
Wash the marjoram, dab dry and chop, except for something to garnish. Add marjoram to the sauce and season with salt and pepper. Pour the sauce over the vegetables and sprinkle with cheese. Bake in a preheated oven (electric: 200 °C/ gas: level 3) for 35-40 minutes until golden brown.
Sprinkle with remaining marjoram and garnish.