Finely chop onion.
Skin and chop tomato.
Chop parsley.
Heat milk.
Peel and slice the aubergines thinly, sprinkle with salt and allow their bitter juices to drain in a colander for at least 1/2 hour. Squeeze, wash in cold water and pat dry. Fry lightly in oil. Remove and drain on absorbent paper.
Fry the onions in 2 T. of oil until pale golden. Add the minced meet and fry until browned. Season with salt and pepper and flawor with allspice or cinnamon (if you like it). Add the chopped tomato, tomato concentrate and parsley. Stir, moisten with a few T of water and simmer for about 15 minutes or until the meat is well cooked and the water absorbed.
Put alternate layers of aubergine slices and meat and onion mixture in a deep backing dish, starting and ending with a layer of aubergines.
Prepare the Bechamel sauce: Melt butter in a saucepan, add flour and stir over low heat for a few minutes until well blended. Add the hot milk gradually, stiring until it boils, taking care not to allow lumps to form. season with salt, pepper and a pinch of nutmeg. Simmer until the sauce thickens. Beat the egg yolk. Stir in a little of sauce and beat well. Pour back into the pan slowly, stirring constantly. Do not allow the sauce to boil again. Pour the sauce over the minced meet and aubergines and bake in a preheated moderate oven (375 F, Mark 4) for about 45 minutes. Serve hot, straight from the dish.