Season and roast the prime rib

• Pat the roast dry and season generously all over with salt and black pepper.
• Rub with olive oil and place on a rack in a roasting tray.
• Roast until the internal temperature reaches 52 °C for medium rare, then rest.

Make the Cajun Parmesan fries

• Toss the potato fries with vegetable oil and Cajun seasoning.
• Spread on a baking tray in a single layer and bake until golden and crisp, turning halfway.
• Sprinkle with grated Parmesan and chopped parsley while still hot.

Prepare the jus

• Sauté the onion, garlic and thyme in the roasting juices until softened.
• Pour in the beef stock and Worcestershire sauce and simmer to reduce slightly.
• Strain and keep warm for dipping.

Slice the meat

• Slice the rested prime rib thinly against the grain.
• Keep the slices warm with a little of the jus.

Assemble the sandwiches

• Toast the split baguettes lightly.
• Spread with horseradish cream and layer the sliced prime rib on top.
• Top with provolone and melt under the grill or in the oven.

Serve

• Serve the sandwiches with the warm jus for dipping and the Cajun Parmesan fries alongside.