This leftover steak sandwich with fresh horseradish sauce is a delicious way to repurpose your leftover steak. The tender and juicy steak is thinly sliced and served on a crusty baguette, topped with a tangy and creamy horseradish sauce. The sauce is made with freshly grated horseradish, mayonnaise, Dijon mustard, and a squeeze of lemon juice, adding a kick of flavor to the sandwich. It's a quick and easy recipe that is perfect for a satisfying lunch or dinner.