With a small sharp knife prick the ham skin all over, make 4 parallel 1/2-inch-deep incisions through the skin the entire length of the ham, and rub the ham lightly with the oil.

In a small bowl rub together the coarse salt, the thyme, the sage, the pepper, and the mustard and rub the mixture over the entire surface of the ham. Put the ham on a roasting rack set in a roasting pan and put the pan in a preheated 500°F. oven. Reduce the temperature immediately to 325°F.> and roast the ham for 1 hour.

 Pour half the beer over the ham, roast the ham for 30 minutes more, and pour the remaining beer over the ham. Roast the ham for 2 1/2 hours more, or until a meat thermometer registers 170°F., and let it cool on the rack in the pan for 15 minutes.

Pull off the brown crisp skin, leaving the layer of fat on the ham, with scissors cut the skin into small pieces, and arrange the cracklings in one layer in a baking pan. Sprinkle the cracklings with salt and bake them in the middle of a preheated 350°F. oven, stirring occasionally, for 15 minutes, or until they are crisp and browned.

Transfer the cracklings to paper towels and let them drain. Cut the remaining fat from the ham, slice the meat thinly across the grain, and arrange it on a platter. Keep the ham warm, covered.

Skim off the fat from the juices in the roasting pan, add 1 cup water, and deglaze the pan over moderate heat, scraping up the brown bits. Transfer the liquid to a saucepan.

In a small bowl whisk together the flour and 1/4 cup of the broth until the flour is dissolved and whisk the mixture into the deglazing liquid with the remaining 3/4 cup broth, the mustard, the sage, the thyme, and the vinegar and pepper to taste, and simmer the gravy, whisking, for 5 minutes.

Garnish the ham with the cracklings and the watercress sprigs and serve it with the gravy.

Servings: 8