01 - Preheat oven to 325°F.
02 - Pat the beef dry and season generously with salt and pepper on all sides.
03 - Heat olive oil in a large Dutch oven over medium-high heat. Sear the roast on all sides until deeply browned, about 4-5 minutes per side. Remove and set aside.
04 - Reduce heat to medium. Add butter and sliced onions. Cook, stirring often, until onions are deeply caramelized and golden brown, about 20-25 minutes.
05 - Stir in garlic and cook for 1 minute until fragrant. Sprinkle flour over onions and cook, stirring constantly, for 2 minutes to eliminate raw flour taste.
06 - Pour in white wine, scraping up any browned bits from the bottom of the pot. Cook until wine is reduced by half, about 2 minutes.
07 - Return roast to the pot. Add beef broth, Worcestershire sauce, thyme sprigs, and bay leaf. Arrange carrots and potatoes around the roast.
08 - Bring to a simmer, cover tightly, and transfer to the oven. Braise for 2.5 to 3 hours, or until beef is fork-tender and easily pulls apart.
09 - Remove roast and vegetables to a serving platter. Discard thyme stems and bay leaf. Skim excess fat from the sauce, then simmer on the stovetop for a few minutes if needed to thicken further.
10 - For a classic French onion finish, sprinkle Gruyère cheese over the roast and broil until melted and bubbly, about 2-3 minutes.
11 - Slice or shred the beef against the grain. Serve with vegetables and ladle the rich gravy over the top. Garnish with fresh chopped parsley.