French Dip Recipe

Cook onions low and slow

Heat a large skillet over medium heat. Add olive oil and 1 tablespoon butter. Once butter foams, add the thinly sliced onions and stir to coat. Cook, stirring occasionally, until soft and beginning to caramelize, about 12–15 minutes.

Deglaze and reduce

Add the red wine to the pan to deglaze, scraping up browned bits. Add the beef stock, brown sugar, balsamic vinegar, salt, and pepper. Reduce heat to medium-low and simmer until liquid is reduced and onions are glossy and jammy, about 12–18 minutes more. Taste and adjust seasoning. Keep warm.

Make the au jus

In a medium saucepan, combine beef stock, red wine, beef demi-glace (or concentrated base), Worcestershire, soy sauce, thyme, salt, and pepper. Bring to a gentle simmer over medium heat, stirring to dissolve the demi-glace. Simmer 8–10 minutes to meld flavors and reduce slightly. Strain if desired for a clear jus. Keep warm over low heat; skim any fat from the surface before serving.

Prepare baguette

Preheat oven to 375°F (190°C). Slice the baguette lengthwise but not all the way through (or fully split if preferred). Spread the softened butter on the cut interior surfaces. Place baguette open-faced on a baking sheet, cut-side up, and toast in the oven 6–8 minutes until lightly golden and crisp.

Warm the prime rib

While the baguette toasts, warm the shaved prime rib in a skillet over medium-low heat just until heated through (about 2–3 minutes) or quickly dip in the warm au jus for 20–30 seconds per handful to heat and impart flavor. Do not overcook; the meat should remain tender.

Assemble sandwiches

Spread an even layer (about 1 tablespoon each side) of Boursin cheese on both interior sides of the toasted baguette. Pile warmed shaved prime rib along the bottom half of the baguette. Top the meat with a generous portion of the red wine onions (about 1/3 to 1/2 cup per sandwich). Place 4 slices of Havarti over the onions and meat. Close the sandwich and press lightly. If you prefer melted cheese, return assembled sandwiches to the oven for 2–3 minutes until Havarti softens.

Slice the sandwich into desired portions (usually 2–3 servings from one baguette). Transfer au jus to small individual dipping bowls. Optional: sprinkle chopped parsley over the sandwich for color. Serve immediately with warm au jus for dipping.