An oven-to-table baking dish, 13 by 9 inches, or any rectangular shape of similar capacity
Detach the Swiss chard stalks from the leaves. Wash both in several changes of cold water.
Trim the stalks into pieces 5 to 6inches long and cut these into strips about ⅓inch wide.
Bring water to a boil in a saucepan, then put in the stalks. Cook until very tender, about 25 to 30 minutes after the water resumes boiling. Drain with a colander spoon—do not empty the water from the pan—and set aside to cool.
Bring the water in the saucepan back to a boil; add a liberal quantity of salt to it; and, as it begins to boil again, put in the Swiss chard leaves. Cook until tender, about 8 minutes at a steady boil. Drain.
Turn on the oven to 400°F.
Put 1½tablespoons of butter in a skillet, turn on the heat to medium high, and when the butter foam begins to subside, add the drained chard leaves together with 2tablespoons of milk, salt, and a generous grinding of pepper. Cook the leaves, turning them over frequently, until they are no longer sopping, about 2 to 3 minutes.
Thinly smear the bottom of the baking dish with butter.
Divide the chard stalks into eight equal bunches. Sprinkle lightly with salt. Wrap each bunch in a slice of bacon and place the bunches in the baking dish, leaving space between.
Divide the chard leaves into small mounds about 2inches thick, and place these in the baking pan in the spaces between the stalk bundles.
To make the béchamel sauce, put the milk in a saucepan, turning on the heat to medium low. Cook until the milk is just short of boiling, reaching the point when it begins to form a ring of small, pearly bubbles.
While you are heating the milk, put the butter in a medium saucepan, turning on the heat under it to low. When the butter has melted completely, stir in all the flour, using a wooden spoon. Continue to cook, stirring constantly, for about 2 minutes. Do not allow the flour to become colored. Remove from heat.
Add the hot milk from the other pan, 2tablespoons at a time, to the flour-and-butter mixture. Stir continuously. As soon as the first 2tablespoons of milk have been incorporated into the mixture, add 2 more, continuing to stir. When, through this procedure, you have put in ½cup milk, you can add the remaining ½cup of milk at one time, stirring steadily, smoothly amalgamating the milk with the flour and butter.
Place the pan over low heat and cook, stirring constantly, until the sauce is as dense as thick cream. If you find any lumps forming, dissolve them by beating the sauce rapidly with a whisk.
Into it stir ⅛teaspoon grated nutmeg and 2tablespoons of grated Parmesan.
Spread the béchamel over the chard stalks and leaves. Sprinkle over it the remaining 3tablespoons of grated Parmesan, and place the dish in the uppermost level of the preheated oven. Bake until the top becomes colored a light gold, about 20 minutes. Let settle down to room temperature before serving.