We wash the aubergines. and we cut them in half lengthwise, we cut them diagonally and put them in a preheated oven at 200º for about 45 minutes. Also we can roast them in the microwave if we want to save time and electricity.
Once they are roasted, we remove the pulp with a spoon and we place the resulting trays in a baking dish. We chop the pulp. Grate the onion and fry it in a large frying pan with three tablespoons of oil. When the onion begins to brown, add the minced meat and sauté well, add the pulp of the aubergines.
Add the flour, stir fry for a few minutes. We pour the milk and cook for a few minutes until we have a creamy dough. Season with nutmeg, salt and pepper.
Fill the aubergines with this mixture, We cover them with the grated cheese and put a piece of butter about each one. Gratin in the oven until the cheese is melted and lightly browned.