French Dip with Caramelized Onion & Gruyère

Season the beef roast generously on all sides with kosher salt and black pepper, pressing the seasoning firmly into the surface. Let it rest uncovered at room temperature for 45 minutes — this promotes an even, deep crust.

Preheat oven to 275°F (135°C). Heat neutral oil in a heavy oven-safe skillet or Dutch oven over high heat until shimmering and just beginning to smoke. Sear the beef roast on all sides — approximately 2 minutes per side — until a deep mahogany crust forms. Do not move the roast until it releases naturally. Remove to a plate and reduce heat to medium.

Add 1 tbsp of unsalted butter to the same skillet. Once foaming subsides, add the sliced yellow onions and 2 sprigs of fresh thyme along with a pinch of salt. Cook over medium to medium-low heat, stirring every 5–7 minutes, until the onions are deeply golden, jammy, and sweet — this takes a genuine 40–50 minutes. Do not rush with high heat. Deglaze with dry sherry or dry white wine, scraping up any fond, and cook until liquid evaporates. Transfer onions to a bowl and reserve the skillet.

Return the seared beef roast to the skillet. Transfer to the 275°F oven and roast until an instant-read thermometer inserted into the thickest part reads 135°F (57°C) for medium-rare to medium — approximately 45–60 minutes depending on thickness. Note: for food safety, if you prefer medium, cook to 145°F (63°C) internal temperature, then rest 3 minutes before slicing.

Remove the beef from the skillet, tent loosely with foil, and rest for 15 minutes. Do not skip resting — the juices must redistribute before slicing.

While the beef rests, build the jus: place the roasting skillet over medium heat. Add 2 tbsp unsalted butter and the smashed garlic cloves; cook 1 minute until fragrant. Add beef stock, Worcestershire sauce, remaining 2 sprigs of fresh thyme, and the bay leaf. Bring to a brisk simmer and reduce by roughly one-third, about 8–10 minutes, until the jus is glossy and concentrated. Taste and adjust salt. Strain through a fine-mesh sieve into a warmed vessel; discard solids.

Set oven to broil. Split the French rolls and, if desired, spread a thin layer of Dijon mustard on the cut sides. Slice the rested beef as thinly as possible against the grain. Pile beef slices onto the bottom halves of the rolls, then top generously with caramelized onions and Gruyère cheese. Arrange open-faced on a sheet pan and broil 2–3 minutes until the Gruyère is melted, bubbling, and lightly spotted. Watch closely — broilers vary.

Close the sandwiches and serve immediately, each accompanied by a small bowl or ramekin of the hot brown jus for dipping. Instruct guests to dip liberally and eat promptly.