Wash the lentils under running cold water, then cook them “al dente” in the broth. Strain the broth and set aside. Let the lentils drain. Wash the tomatoes and chop them. Wash and clean the cabbage, cut it into thin strips, put it in a strainer and wash it under cold running water. Peel the onions and chop. Heat the olive oil in a large pan and brown the onion over moderate heat, add the lentils, tomatoes and cabbage. Pour about 100 ml of the stock and cook for about 10 minutes over moderate heat. Season with salt and pepper and season with the chopped parsley. For the béchamel sauce, melt the butter in a pan, add the flour, stir, then pour the milk and about 200 ml of the broth previously set aside. Cook and thicken for about 5 minutes over moderate heat, stirring. Season with salt and nutmeg. Heat the oven to 180°C with ventilation. Fill a pastry mould in layers with the béchamel sauce, the sheets of lasagna and the contents of the pan. Finish with a layer of béchamel sauce. Sprinkle with cheese and cook in the hot oven for 35 minutes.