Heat the oil in the pan and pass the finely chopped onion until golden brown. Put the minced meat and fry, stirring, until the meat is cooked. Season with salt and pepper.
Add the trade wind or tomatoes, stir and cook over low heat for about 10 minutes. Then combine the mass with basil.
In a skillet, melt butter over moderate heat. Stir in the flour while stirring with a whisk. Continuing to whip the mixture, gradually pour in the milk. Boil the bechamel sauce, stirring constantly, until it thickens. Season with salt, pepper and nutmeg.
Grease a baking dish. Put a few sheets of lasagna on the bottom and cover them with a portion of the sauce. Distribute the top part of the meat filling. Repeat layers. The top should be bechamel sauce, sprinkled with grated parmesan cheese. Bake for 30 minutes at 190 ° C.