01 - Set the oven to 320°F.
02 - Pat the steaks dry, season generously with salt and black pepper, then dust lightly with flour.
03 - Heat vegetable oil in a large ovenproof casserole over medium-high heat. Sear the steaks for 2 to 3 minutes on each side until browned. Remove and set aside.
04 - Add sliced onions, carrots, celery, and minced garlic to the same pan. Sauté for about 5 minutes until softened.
05 - Stir in tomato paste and cook for 1 minute.
06 - Pour in red wine if using, scraping up any browned bits from the pan. Simmer gently for 2 minutes.
07 - Return the steaks to the pan. Add beef stock, Worcestershire sauce, thyme, and bay leaves. Bring the mixture to a gentle simmer.
08 - Cover the casserole tightly and transfer to the oven. Braise for 2 hours, turning the steaks once halfway through, until the meat is very tender.
09 - Remove thyme sprigs and bay leaves. Taste and adjust seasoning as needed. Serve the steaks with the braising gravy and vegetables.