Prepare the raw artichoke hearts. Break off the stem (do not cut it) about 1 inch from the base. Cut off the large leaves just above the edible part. Peel the base of the artichoke, removing the stiff parts, then cut the stem off right at the base. Rub with lemon juice to avoid the artichokes turning brown. Scoop the choke out using a sharp spoon. Rub with lemon juice. Cook in boiling salted water, adding some lemon juice in the water. When you can slide a knife blade through the artichoke hearts, stop cooking. Drain and lay hollow side up in a gratin dish. Coat in highly seasoned white sauce, flavored with nutmeg and mixed, at the last minute, with the grated Swiss and Parmesan cheese. Bake in a hot oven coloring the surface as the gratin reaches a boiling temperature.
