French Dip Recipe

Thinly slice prime rib

Partially freeze the cooked prime rib (about 30–45 minutes) until firm but not rock hard. Using a sharp slicing knife, slice the roast as thinly as possible against the grain into about 1–2 mm slices. Keep slices chilled on a tray covered loosely with plastic while you assemble other components.

Prep rolls

Preheat broiler to high (or set oven to 400°F / 200°C with a rack near top). Split sourdough hoagie rolls lengthwise, leaving a hinge if desired. Spread 1/2 tablespoon softened butter evenly inside each roll and season lightly with a pinch of kosher salt and a grind of black pepper.

Assemble sandwiches

Place generous overlapping layers of thinly sliced prime rib into each bottom half (about 300 g total meat divided across 4 rolls). Top the warm meat with two slices of Havarti each. If you prefer the cheese melted, place assembled open-faced sandwiches under the broiler for 30–60 seconds until cheese just softens and begins to bubble—watch closely to avoid burning. Spread about 1 tablespoon horseradish crème on the top half of each roll, then close sandwiches.

In a small bowl combine prepared horseradish, sour cream, mayonnaise, lemon juice, Dijon mustard and chopped chives. Season with 1/4 teaspoon salt and 1/4 teaspoon freshly ground black pepper. Taste and adjust—add more horseradish for heat or more sour cream to mellow. Refrigerate until ready to use. Yields roughly 3/4 cup enough for 4 sandwiches.

Make the au jus while the fries cook so it's hot when serving. In a medium saucepan over medium heat, melt 1 tablespoon butter. Add minced shallot and smashed garlic clove and sweat until translucent and fragrant, about 2 minutes—do not brown. Add red wine and simmer 2–3 minutes to reduce slightly.

Add beef drippings or stock, Worcestershire sauce, soy sauce, thyme sprig and bay leaf. Bring to a gentle simmer and reduce by about 10–15 minutes to concentrate flavor slightly (you should end with roughly 3 to 3.5 cups). Season with 1/2 teaspoon salt and 1/4 teaspoon black pepper. Remove thyme sprig, bay leaf and garlic. Keep warm in a small pot on very low heat or reheat just before serving. Strain through a fine-mesh sieve into a warmed gravy boat if desired.

Prepare potatoes: Cut peeled russets into very thin (about 2–3 mm) shoestring matchsticks. For best texture, rinse cut fries under cold water until water runs clear to remove starch. Drain and pat completely dry with clean kitchen towels or paper towels—moisture will cause oil spatter and soggy fries.

Heat beef tallow: In a heavy-bottomed pot or deep fryer, heat beef tallow to 325°F (163°C) for the first blanch fry. Use a thermometer to monitor temperature. Fry the shoestrings in batches so they don’t crowd the oil—blanch 2–3 minutes until pale and limp but not browned. Remove with a spider or slotted spoon and drain on a wire rack over a sheet pan. Let rest 5 minutes.

Second fry and season: Increase oil temperature to 375°F (190°C). Return blanched fries to the hot tallow in batches and fry until golden brown and crisp, about 1–2 minutes. Drain on a rack lined with paper towels or on a wire rack. Immediately season with fine sea salt and a light grind of black pepper while hot. Keep warm in a single layer in a low oven (200°F / 95°C) if making ahead briefly.