Ingredients:

  • 4 cups low sodium Beef Stock
  • 2 tbsp Worcestershire Sauce
  • 1 tsp Dried Thyme
  • 1 clove Garlic, smashed
  • 1/2 tsp Salt
  • 1/4 tsp Black Pepper
  • 1/2 cup Mayonnaise or Crème Fraîche
  • 2 tbsp Prepared Horseradish (drained)
  • 1 tsp Lemon Juice
  • Pinch of Salt (for cream)
  • 1 large Yellow Onion, thinly sliced
  • 2 tbsp Unsalted Butter
  • 1 lb Leftover Prime Rib, thinly sliced
  • 1 large Baguette (sliced into 4 portions)
  • 8 slices Provolone Cheese (or Swiss)
  • 1 tbsp Olive Oil (for brushing bread)

Instructions:

  1. Start the Au Jus: Combine beef stock, Worcestershire sauce, thyme, garlic, salt, and pepper in a medium saucepan. Bring to a boil, then immediately reduce heat to a low simmer. Allow to reduce by approximately one-quarter while preparing the other elements, concentrating the flavor.
  2. Caramelize the Onions: Melt butter in a large skillet over medium-low heat. Add the thinly sliced onions and cook slowly for 20-25 minutes, stirring occasionally, until deeply golden brown and sweet. Remove from heat and set aside.
  3. Prepare the Meat and Cream: While onions are caramelizing, slice the prime rib as thinly as possible. In a small bowl, combine mayonnaise, prepared horseradish, lemon juice, and a pinch of salt to make the Horseradish Cream; mix until smooth and refrigerate.
  4. Toast the Bread: Preheat the broiler. Slice the baguette portions lengthwise. Brush the insides lightly with olive oil. Place the bread cut-side up on a baking sheet and toast under the broiler for 1-2 minutes until lightly golden and crisp.
  5. Assemble: Layer the bottom half of each baguette with a generous spread of caramelized onions. Layer the thinly sliced prime rib over the onions. Place two slices of Provolone cheese on top of the meat.
  6. Melt the Cheese: Return the open-faced sandwiches to the baking sheet. Place under the broiler for 2-3 minutes until the cheese is bubbling and melted.
  7. Serve: Close the sandwiches. Divide the hot Au Jus among small dipping bowls. Serve the Prime Rib Melts immediately alongside the Au Jus and Horseradish Cream.