What To Do
1. Toast: Split the rolls and spread with butter. Lightly toast under a broiler until edges are golden.
2. Warm the beef: Heat the au jus in a skillet. Dip the roast beef slices into the hot liquid for 30 seconds to warm them through.
3. Assemble: Pile the warm beef onto the rolls and top with several slices of Horseradish Cheddar.
4. Melt: Place the open-faced sandwiches under the broiler for 1-2 minutes until the cheese is bubbling and molten.
5. Serve: Serve with individual cups of the hot au jus for dipping.