1.In A Small Skillet, Saute Onion In Oil Until Tender. Meanwhile, In A Large Saucepan, Bring The Vegetable And Beef Broth To A Boil; Stir In The Horseradish, Worcestershire Sauce, Mustard And Celery Salt. Add The Corned Beef, Sauerkraut And Onion. Reduce Heat To Low; Cover And Simmer For 10 Minutes. 2.Ladle Soup Into Four Ovenproof Bowls; Top With Bread Cubes And Swiss Cheese. Broil 3-4 In. From The Heat For 2-3 Minutes Or Until Cheese Is Melted.