Prime Rib French Dip Recipe

Roast the prime rib

Preheat oven to 325°F (160°C). Pat the prime rib dry and season evenly on all sides with 2 tsp kosher salt and 1 tsp freshly ground black pepper. Heat 2 tbsp olive oil in a large ovenproof skillet or roasting pan over medium-high heat until shimmering. Sear the roast, fat-side down first, 3–4 minutes per side until deep golden brown (including ends). Remove from heat.

Roast to temperature

Insert a probe thermometer into the thickest part of the roast. Place roast in the oven and roast until internal temperature reaches 125°F (52°C) for medium-rare, about 1 to 1½ hours depending on size. Remove roast, tent loosely with foil, and let rest 20–30 minutes (temperature will rise slightly). Reserve juices that accumulate for the au jus.

Make the au jus

While roast rests, pour off excess fat from the roasting pan leaving browned bits. Place the pan over medium heat, add 1 cup dry red wine to deglaze, scraping up browned bits with a wooden spoon. Add 6 cups beef broth, 1 cup beef demi-glace (if using), 4 smashed garlic cloves, 4 thyme sprigs and 2 bay leaves. Bring to a simmer and reduce gently 10–12 minutes. Taste and adjust seasoning with additional salt or pepper if needed. Strain the au jus through a fine mesh sieve into a bowl or small saucepan and keep warm (hold on very low heat).

Shave the prime rib

Using a sharp carving knife or meat slicer, thinly slice (shave) the rested prime rib across the grain into very thin slices. Aim for approximately 2 lbs of shaved meat for sandwiches. Keep sliced meat warm by loosely covering with foil or placing briefly in the warm au jus to poach lightly if desired.

Heat 1 tbsp olive oil and 2 tbsp unsalted butter in a large skillet over medium-high heat until butter foams. Add the thinly sliced onion and cook, stirring occasionally, 6–8 minutes until translucent and starting to caramelize.

Add the sliced mushrooms to the pan, sprinkle with 1 tsp salt, 1/2 tsp black pepper and 1 tsp chopped fresh thyme. Continue to cook 6–8 minutes until the mushrooms release their moisture and both mushrooms and onions are deeply browned and tender. Taste and adjust seasoning. Keep warm until assembly.

Preheat broiler (or oven to 450°F/230°C). Split the baguette or hoagie rolls and butter cut sides lightly with the 3 tbsp softened butter. Place cut-side up on a baking sheet and toast under the broiler 1–2 minutes until golden — watch carefully to avoid burning.

Pile approximately 6 oz (by weight) shaved prime rib onto each roll bottom. Spoon a generous portion of sautéed mushrooms and onions over the meat. Drape 2 slices of pepper jack cheese over the top.

Place assembled sandwiches under the broiler 1–2 minutes until cheese melts and edges of the roll are crisp. Alternatively, place in a 400°F (200°C) oven for 3–5 minutes.

Serve each sandwich hot with a warmed cup or small bowl of au jus for dipping. Optionally, spoon a few tablespoons of warmed au jus directly over the meat before topping with cheese for extra moisture and flavor.