Cut the sausage links into 3/4-inch slices, keeping hot and sweet sausages separate. Cover the sausages with water in separate saucepans and bing to a boil. Reduce heat so that water barely simmers. Cook 15 to 20 minutes. A lot of fat will come out of the sausages, making them crisper and more appealing. Drain thoroughly. Mix cranberry sauce and mustard well. Taste. Use more mustard if you wish. Cover tightly and store in the refrigerator in a pretty dish until needed. When you are alnost ready to serve, put sausage slices on a rack over a shallow pan with sides and run under the broiler just until crisp and lightly browned. Turn and brown the other side. Arrange hot sausage on one end of a platter, sweet sausage on the other, and the sauce in the middle. Spear the sausage slices with cocktail toothpicks and make sure there are small plates or plenty of napkins available.