French Dip Sandwich Recipe

Prepare prime rib

If using leftover or pre-roasted prime rib, thinly slice across the grain into roughly 1/8–1/4-inch slices. Keep the slices chilled until ready. If starting from raw roast, roast to desired doneness, rest 20–30 minutes, then thinly slice.

Reheat and season meat

In a large skillet over medium-high heat, add 1 tbsp vegetable oil and warm until shimmering. Add sliced prime rib in a single layer (work in batches to avoid crowding) and sear briefly, about 30–60 seconds per side, just to warm through and develop color. Remove to a plate and keep warm; reserve any pan juices for the au jus.

Prepare rolls

Preheat broiler to high (or oven to 500°F/260°C on a high rack). Mix softened butter with minced garlic. Split the French rolls and brush the cut sides lightly with garlic butter. Toast under the broiler just until golden, 1–2 minutes — watch closely to avoid burning.

Assemble and broil with Gruyère

Fill the bottom halves of the rolls with an even portion of warmed prime rib (about 4 oz meat per sandwich). Pile slices or shreds to create height, then top each with a generous sprinkle of grated Gruyère (about 1/3 cup per sandwich). Place assembled open sandwiches on a sheet pan and broil 2–4 inches from the element until cheese is melted and lightly browned, about 2–4 minutes. Remove from oven and top with the roll lids.

In a medium saucepan, melt 1 tbsp butter over medium heat. Add the finely chopped shallot and sauté 1–2 minutes until softened but not browned.

Add the optional red wine to deglaze the pan, scraping up browned bits; simmer 1–2 minutes until reduced by about half.

Pour in the beef stock, reserved pan drippings or beef base, soy sauce, and Worcestershire sauce. Add the thyme sprig. Bring to a gentle simmer and let the flavors meld for 8–10 minutes.

For a slightly thicker, glossy jus: mix 1 tsp cornstarch with 1 tbsp cold water to make a slurry. Whisk the slurry into the simmering au jus and cook 1–2 minutes until slightly thickened. Taste and season with 1/2 tsp salt and 1/4 tsp black pepper (adjust to taste). Strain the au jus through a fine mesh sieve into a warm serving vessel and keep hot.

In a small bowl, combine 3 tbsp prepared horseradish, 1/2 cup sour cream, 1/4 cup mayonnaise, 1 tsp Dijon mustard and 1 tsp lemon juice. Whisk until smooth.

Season with 1/4 tsp salt and 1/8 tsp black pepper. Stir in chopped chives if using. Taste and adjust heat or acidity by adding more horseradish or lemon as desired. Chill until service; serve alongside sandwiches.

Rinse the thin potato slices under cold water then drain and pat very dry with clean kitchen towels or paper towels to remove excess surface starch (this prevents oil sputter and helps crisping).

In a heavy-bottomed pot or deep fryer, heat 2 cups neutral oil to 350°F (177°C). If you don't have a thermometer, test a single slice — it should sizzle steadily.

Fry the potato slices in small batches (avoid overcrowding) for 2–4 minutes until crisp and golden. Use a slotted spoon to transfer chips to a paper-towel-lined tray. Immediately season with kosher salt, a pinch of black pepper and smoked paprika (if using).

Keep chips in a single layer to preserve crispness; serve warm or at room temperature alongside the sandwich.