1. Cut the eggplants in half lengthwise and carefully remove the flesh by scraping with a spoon.
2. Chop the onions and sauté for 3 minutes in 2 tablespoons of oil. Add the ground beef, cook for 3 minutes, then add the eggplant flesh, diced tomatoes, cognac, parsley, salt, and pepper. Cook for another 3 minutes.
3. Melt the butter in a saucepan, add the flour, mix, and cook for 2 minutes over low heat. Pour in the hot milk and cook for another 4 minutes while whisking. Sprinkle with half of the grated cheese, nutmeg, and salt.
To finish, distribute half of the béchamel sauce in the eggplant shells, add the ground beef, and finish with a layer of béchamel sauce, sprinkle with the remaining grated cheese. Bake for 20 minutes in a preheated oven at 220°C. Garnish with dill.