Our favorite way to use leftover prime rib is piling it on French loaf with caramelized onions and classic horseradish sauce.
Substitute fresh baby spinach for the arugula.
Use sweet yellow onions such as Vidalia or Walla Walla in this recipe.
Horseradish cream can be found in the condiment or dairy aisle in your favorite grocery store. Or make your own: Stir 1 cup sour cream, 2 tablespoons fresh ground horseradish, 1 tablespoon chopped fresh chives and 1/4 teaspoon coarsely ground pepper until well blended.