The Ultimate Leftover Prime Rib Sandwich Recipe

I still remember the thrill of opening the fridge after holiday dinner, staring at that glorious leftover prime rib, wondering how to make it feel new again. That’s when I created what I now call the Ultimate Leftover Prime Rib Sandwich—a simple, gourmet way to transform those treasured slices into a steakhouse-quality meal. Trust me, this sandwich turns every scrap into pure comfort.

Table of Contents

Why This is the BEST Leftover Prime Rib Sandwich

• Impossibly Tender Meat Reimagined: By thinly slicing and gently warming leftover prime rib, the sandwich keeps every bite juicy and tender—never dry or chewy.
• Rich, From-Scratch Au Jus: Our 15-minute au jus brings savory depth and the perfect dunking sauce, making each mouthful feel indulgent and restaurant-worthy.
• Choice of Horseradish Sauces: Whether you want classic creamy, punchy deli-style, or garlic-herb infused, this recipe offers three horseradish sauce options to tailor the sandwich to your taste.
• Garlicky, Toasted Bread: A crusty baguette, toasted just right with garlic butter, provides the perfect sturdy base. It won’t sog out when dipped, keeping your sandwich crisp and flavorful.

Key Ingredients for a Perfect Sandwich

Each ingredient was carefully selected for its role in creating a harmonious, satisfying experience:

• Prime Rib: Thinly sliced to showcase tenderness and flavor without overwhelming the sandwich.
• Sweet Onion & Mushrooms: Caramelized for deep sweetness and umami richness.
• Arugula: Adds a peppery bite that balances richness and elevates freshness.
• Baguette or Hoagie Rolls: A crusty, sturdy bread like a baguette is essential because its firm crumb won’t get soggy when dunked in the au jus.
• Creamy Horseradish Sauce: Adds tangy heat, cutting through the meat’s richness.

Cheese	Flavor Profile
Provolone	Mild, creamy, and slightly nutty
Swiss	Sweet, nutty, melts smoothly
Smoked Gouda	Rich, smoky, adds depth
Pepper Jack	Spicy, creamy with a jalapeño kick

Having your mise en place lined up, especially with your chosen cheese and sauces ready, makes building this sandwich a breeze.

The Horseradish Sauce Trio (Choose Your Favorite!)

1) Classic & Creamy

A smooth, mellow option blending horseradish with mayonnaise, sour cream, and a hint of lemon juice for tang.

2) Extra-Pungent Deli-Style

For those who love a sharp kick, this uses prepared horseradish, a splash of vinegar, and Dijon mustard for a bold, spicy punch.

3) Garlic & Herb Infused

Combines horseradish with fresh garlic, chopped parsley, and chives for a fragrant, savory twist perfect for herb lovers.

These sauces bring versatile layers of flavor, allowing you to customize your leftover prime rib sandwich just how you like it.

Ingredients

• 1 lb leftover prime rib (thinly sliced)
• 1 large sweet onion (sliced)
• 8 oz mushrooms (sliced)
• 1 cup arugula
• 1 baguette (or hoagie rolls)
• 1 cup beef broth
• 1 tbsp apple cider vinegar
• ½ cup creamy horseradish sauce (see recipe)

The 15-Minute Rich Au Jus (A Game-Changer)

Ingredients:

• Beef broth
• Worcestershire sauce
• Aromatics (like garlic, onion, and fresh herbs)

Instructions:

1. Combine broth, Worcestershire sauce, and aromatics in a saucepan.
2. Simmer gently for 15 minutes to concentrate flavors.
3. Strain and keep warm for dipping and reheating the meat.

This au jus is the secret to steakhouse-worthy sandwiches, tenderizing the meat gently while boosting every bite with savory goodness.

How to Make the Perfect Leftover Prime Rib Sandwich

1. Prepare your horseradish sauce by mixing the sauce ingredients together in a small bowl and refrigerate until needed.
2. Melt 2 tablespoons of butter in a large skillet.
3. When the butter is melted, add the sliced onions and mushrooms to the pan.
4. Saute the onions and mushrooms over high heat until they begin to brown. Let them cook for 3-5 minutes without moving them around, so they have a chance to begin the caramelization process.
5. Turn the mushrooms and onions over and reduce to medium heat and let them continue to cook for another 5-7 minutes. Stir them around during this part of the process.
6. While the mushrooms and onions are cooking, trim the leftover prime rib. Remove the bone and extra fat from the edges of the meat. Take out any fat deposits from the middle of the beef.
7. Slice the baguette in half lengthwise so you make a top and bottom.
8. Slather a good amount of creamy horseradish sauce on the bottom side of French bread.
9. Add a good handful of arugula (the peppery flavor of arugula improves the overall flavor of the sandwich).
10. Place thinly sliced prime rib on top of the arugula (fold the meat, setting it side by side so it’s not just lying on top of each other).
11. Add the caramelized onions and mushrooms to the sandwich.
12. Add a few slices of provolone cheese (or Swiss cheese) to the sandwich for additional flavor. For melted cheese, add the slices before warm mushrooms and onions so the heat melts it.
13. Cover with the top of the baguette and cut into sandwiches. Serve with hot beef broth, apple cider vinegar, and extra horseradish sauce.

Leftover Prime Rib Sandwich Variations & Cooking Methods

Variation	Instructions
Panini-Style	Assemble sandwich and grill in a skillet with a weight until bread is crispy and cheese melts.
Sandwich Sliders	Use small rolls and miniaturize the assembly for party-friendly bites.
5-Minute Assembly	Use store-bought horseradish sauce and pre-cooked veggies for a quick fix.
Air Fryer Method	Toast assembled sandwich in the air fryer at 375°F for 5 minutes to melt cheese and crisp bread.
Grill Method	Wrap sandwich in foil and heat on a grill for 7-10 minutes, turning once to warm through.

What to Serve with Your Sandwich

Classic sides amplify the steakhouse vibe and balance the rich sandwich:

• Crispy French fries or sweet potato fries (try one of my air fryer recipes )
• A simple green salad with a tangy Simple Vinaigrette Dressing
• Or switch things up with other leftover prime rib ideas

These pairings bring texture and freshness and round out your meal perfectly.

Expert Tips & Troubleshooting

How to Keep Well-Done Prime Rib Tender

Gently warm sliced prime rib in hot au jus for just 30-60 seconds instead of cooking it longer. This reheats without drying or toughening the meat.

How to Prevent a Soggy Sandwich

Toast your bread well and add cheese beneath the caramelized veggies as a moisture barrier. This ensures every bite remains crisp, even when dunking. For a comprehensive guide on preventing soggy sandwiches, check out this resource on proper sandwich construction techniques.

Storage and Freezing

Slice leftover prime rib before freezing. Stack portions separated by parchment paper in a freezer-safe bag. This keeps slices ready for quick sandwich assembly later.

Frequently Asked Questions (FAQ)

What’s the best bread for a prime rib sandwich?

A crusty baguette or a sturdy hoagie roll is best because it holds up to au jus without falling apart.

Can I prepare these sandwiches in advance?

You can prep ingredients ahead, but assemble right before serving to prevent sogginess.