Prepare the roast: Pat the beef roast dry with paper towels. This ensures a better sear and helps the seasonings adhere.
Create the rub: In a small bowl, combine minced garlic, chopped rosemary, thyme leaves, salt, pepper, mustard powder, and paprika. Add olive oil to create a paste.
Season the meat: Rub the paste all over the roast, making sure to cover all sides evenly. If time permits, let the seasoned roast sit at room temperature for 30 minutes to absorb the flavors.
Sear the roast (optional but recommended): Heat a large skillet over medium-high heat. Add a tablespoon of oil and sear the roast on all sides until browned, about 3-4 minutes per side. This step adds tremendous flavor.
Prepare the slow cooker: Place the quartered onions, carrots, and celery in the bottom of the slow cooker to create a flavorful bed for the roast.
Add the roast: Place the seared roast on top of the vegetables.
Prepare the cooking liquid: In a bowl, whisk together beef broth, red wine, Worcestershire sauce, balsamic vinegar, and tomato paste. Pour this mixture around (not over) the roast to avoid washing off the seasonings.
Add bay leaves: Tuck bay leaves into the liquid around the roast.
Cook: Cover and cook on LOW for 8 hours (preferred) or on HIGH for 4-5 hours. For the most tender results, the low and slow method is recommended.
Check for doneness: The roast is done when it's fork-tender but still holds its shape. For medium-rare to medium doneness, the internal temperature should read 135-145°F (57-63°C).
Rest the meat: Remove the roast to a cutting board, tent loosely with foil, and let rest for 15-20 minutes before slicing. This crucial step allows the juices to redistribute throughout the meat.
Prepare the gravy (optional): Strain the cooking liquid, skim off excess fat, and simmer in a saucepan until reduced by about one-third. Thicken with a cornstarch slurry if desired (1 tablespoon cornstarch mixed with 2 tablespoons cold water).
Slice and serve: Slice the roast against the grain and arrange on a serving platter. Garnish with fresh rosemary sprigs for a festive touch. Serve with the gravy on the side.
