In a small bowl combine brown sugar, softened butter, corn syrup, nutmeg, and cardamom. Set aside. Tear off a 36x18-inch piece of heavy foil. Fold in half to make a double thickness of foil that measures 18x18 inches. Place pear slices in the center of the foil. Spoon brown sugar mixture atop pears. Sprinkle with nuts. Bring up two opposite edges of foil and seal with a double fold. Fold ends to completely enclose the pears, leaving space for steam to build. Place foil packet on grill rack of an uncovered grill directly over medium coals for 12 to 15 minutes or until pears are tender. Serve warm pear mixture with ice cream or shortcake, if desired. Makes 4 to 6 servings.