Dry a bone-in, fully cooked half ham (do not use a country ham) and bring to room temperature. Preheat the oven to 375 degrees F. Trim the ham skin, leaving the fat intact. Score the fat in a crosshatch pattern, making the cuts about 3/4 inch deep and 1 inch apart. Put the ham flat-side down on a rack in a roasting pan; add 1 cup water. Bake on the lowest oven rack, 40 minutes, adding more water if the pan gets dry. Meanwhile, make the glaze: Whisk 1 cup jam or marmalade with 3/4 cup brown sugar, 1 cup dijon mustard, 2 tablespoons cider vinegar and 2 teaspoons Worcestershire sauce. Brush the ham with half of the glaze; cover loosely with foil and bake 45 more minutes. Brush with the remaining glaze and bake, uncovered, until the glaze is browned, 40 to 50 more minutes. Let rest 15 minutes before carving.
Don't toss your ham bone! Add it to simmering soups, beans or braised greens for extra flavor.
Give your ham a great crunch: Sprinkle one of the below mixes onto the glaze before the last 40 to 50 minutes of cooking.
Spring Herb Mix 1 cup panko (Japanese breadcrumbs), 3 tablespoons each chopped parsley and chives, and the grated zest of 1 lemon.
Cornmeal-Thyme Crush 1 cup cornbread stuffing mix; toss with 2 tablespoons chopped thyme, 1 1/2 teaspoons ground coriander and 1/2 cup cornmeal.
Spicy Sourdough Grind 3 cups cubed sourdough bread in a food processor; toss with 1 tablespoon chili powder and 1 bunch chopped scallions.