Method
Make sour cream sauce. Combine sour cream, horseradish, chives, mustard and salt in bowl. Cover and refrigerate until ready to use.
Cut beef rib roast slices into strips. Place beef strips in hotel pan with au jus. Keep warm on steam table. For each serving: split and fluff 1 potato; ladle 2 Tbsp au jus over potato. Top with 1/4 cup sour cream sauce, 4 oz sliced beef and additional 1 Tbsp au jus. Sprinkle with 1 oz cheese. Garnish with chopped chives. Accompany with additional 1/4 cup sour cream sauce in ramekin.