01 - Preheat oven to 325°F. Pat the beef thoroughly dry with paper towels, then season generously with kosher salt and black pepper on all sides.
02 - Heat olive oil in a large Dutch oven over medium-high heat. Sear the roast on all sides until deeply browned with a rich crust, approximately 4–5 minutes per side. Remove beef and set aside on a plate.
03 - Reduce heat to medium. Add butter and sliced onions to the pot. Cook, stirring frequently, until onions are deeply caramelized and golden brown, about 20–25 minutes.
04 - Stir in minced garlic and cook for 1 minute until fragrant. Sprinkle flour over the caramelized onions, stirring constantly to coat, and cook for 2 minutes to remove raw flour taste.
05 - Pour in white wine while scraping up any browned bits from the bottom of the pot with a wooden spoon. Simmer until wine is reduced by half, approximately 2 minutes.
06 - Return the seared roast to the pot. Add beef broth, Worcestershire sauce, fresh thyme sprigs, and bay leaf. Arrange carrots and potatoes around the roast, submerging them partially in the liquid.
07 - Bring the mixture to a gentle simmer, cover tightly with the lid, and transfer to the preheated oven. Braise for 2.5–3 hours until beef is fork-tender and easily pulls apart.
08 - Remove the roast and vegetables from the pot. Discard thyme stems and bay leaf. Skim excess fat from the sauce surface and simmer briefly if thickening is desired. For optional French onion finish, sprinkle Gruyère over the beef and broil until melted and bubbly. Slice or shred the meat and serve with vegetables ladled with rich gravy.