Place brisket on aluminum foil. Spread each side of the brisket with prepared mustard and whole mixed pickling spices. Wrap foil tightly around brisket and place in 8 x 10 baking dish. Bake in slow oven (225 degrees F.) 3.5 hours or until done. Remove brisket from foil. Scrape off and discard pickling spices from brisket and trim any excess fat. Cut brisket into 4 to 6 equal portions and place in 8 x 10 baking dish. Rinse and drain sauerkraut and place on top of brisket. Sprinkle with grated swiss cheese. Place under the broiler until the cheese has browned, about 8 to 10 minutes. Garnish with prepared mustard.