Place ham on a rack in a shallow roasting pan. Using a sharp knife, score surface of ham with 1/4 inch deep cuts in a diamond pattern; insert a clove in each diamond. Cover and bake at 325 for 2 to 2 1/2 hrs.
Meanwhile, in a large saucepan, dissolve cornstarch in water; stir in 2 cups dark brown sugar, pineapple, lemon juice, mustard and salt. Bring to boil; cook and stir for 1-2 minutes or until slightly thickened. Reserve 2 cups for sauce, keep warm.
Remove the ham from oven. Increase oven to 425. Pour the remaining pineapple mixture over ham. In small bowl, mix light brown sugar and remaining dark brown sugar; spread over ham.