French Dip Prime Rib Sandwiches with Swiss & Horseradish Aioli Step-by-step instructions

Before you start

Before you begin, have all your ingredients ready: the prime rib shaved, the French rolls split, the onion caramelized, and the Swiss cheese sliced. Make the horseradish aioli first and keep it chilled.

Heat the beef consommé in a large skillet over medium heat so it is simmering when you add the beef. Preheat the broiler with a rack about 6 inches from the heat source. This recipe moves quickly once you start assembling, so having everything prepped and within reach is essential.

Instructions

Prep and Warm the Beef

1. 1Make the Horseradish Aioli
   In a small bowl, combine the mayonnaise, prepared horseradish, Dijon mustard, and lemon juice. Whisk until smooth and well blended. Set aside in the refrigerator while preparing the other components.
   Look for The aioli should be creamy and slightly pinkish from the horseradish, with a zesty aroma.
   Tip For a sharper kick, add an extra 1/2 teaspoon of prepared horseradish. Taste and adjust before assembling.
2. 2Warm the Beef in Au Jus
   Pour the beef consommé into a large skillet and bring to a simmer over medium heat. Add the thinly shaved prime rib in a single layer and let it warm for 30 seconds, turning gently with tongs, until heated through and saturated with the broth. Let it rest for 3 minutes before slicing.
   Look for The beef should be steaming and glistening with broth, but not boiling aggressively.
   Safe temperature 145°F (63°C) internal temperature (steaks, chops and roasts)
   Tip Keep the beef in the jus only briefly—overcooking can make it tough. Work in batches if needed.

The aioli should be smooth and creamy, with a noticeable horseradish aroma. The beef is warming in the jus, turning from pink to a deeper brown as it absorbs the broth. The kitchen smells savory and rich, with a hint of tang from the horseradish. The beef should be heated through but still tender and juicy. Check that the jus is simmering gently and not boiling rapidly.

Assemble and Melt

3. 3Toast the Rolls
   Preheat the broiler. Place the split French rolls cut-side up on a sheet pan and toast under the broiler for 1–2 minutes, until golden and crisp at the edges. Keep a close eye to prevent burning.
   Look for The rolls should be lightly browned and crisp, with a soft interior.
   Tip If the rolls are very fresh, toasting helps them hold up to the dipping without becoming soggy.
4. 4Assemble the Sandwiches
   Spread a generous layer of the horseradish aioli onto the cut sides of each toasted roll. Pile the warm prime rib evenly onto the bottom halves, then top with the caramelized onions. Lay 2 slices of Swiss cheese over the top of each sandwich, covering the beef and onions completely.
   Look for The sandwiches should be tall and packed, with cheese draped over the edges.
   Tip Use the aioli generously—it balances the richness of the beef and adds tang.
5. 5Broil Until Bubbly
   Return the assembled sandwiches to the broiler and cook for 2–3 minutes, until the Swiss cheese is melted and bubbly with golden spots. Watch closely to avoid burning the bread.
   Look for The cheese should be fully melted and lightly browned in spots, and the edges of the rolls may darken slightly.
   Tip If the cheese needs more time, lower the rack or reduce the broiler heat to prevent the bread from scorching.

The rolls are toasted to a golden crisp. The sandwiches are piled high with beef and onions, and the cheese is just starting to soften. The aioli adds a creamy white layer against the dark beef.

The sandwiches look hearty and inviting. When you slide the pan under the broiler, you should see the cheese bubble and turn golden in spots. The edges of the rolls may darken slightly—that's fine.

Slice and Serve

6. 6Dip and Serve
   Remove the sandwiches from the broiler and let them rest for 1 minute. Slice each sandwich in half diagonally with a serrated knife. Serve immediately with the remaining hot beef consommé on the side for dipping.
   Look for The sandwiches should be steaming, with melted cheese stretching as you slice.
   Tip Serve the jus in small bowls for each person—it’s the star of the dish.

The sandwiches are out of the broiler, with melted cheese stretching as you slice. The jus is still steaming in its bowl. The first bite should have a satisfying crunch from the toasted bread, followed by the tender beef and creamy aioli. The cheese is gooey and rich. The overall experience is messy in the best way, with jus dripping down your fingers.

Common mistakes

One common mistake is overcooking the beef in the jus, which can make it dry and tough. Keep the heat at a gentle simmer and only warm the beef for about 30 seconds.

Another pitfall is using too much aioli, which can make the sandwich soggy—spread a thin, even layer. Also, watch the broiler closely; bread can burn quickly. If the cheese isn't melting fast enough, move the rack closer to the heat, but keep an eye on it.

How to tell it’s done

The beef is done when it is heated through to at least 145°F (63°C) after warming in the jus. It should be steaming and glistening with broth, but still tender and pink in the center.

The Swiss cheese should be fully melted and bubbly, with golden brown spots on the surface. The rolls should be toasted and crisp on the edges, yet soft enough to bite through. The au jus should be hot and steaming when served.

• Steaks, chops and roasts: 145°F (63°C) in the thickest part, then a 3-minute rest