Prepare the Roast:
Preheat your oven to 300°F (150°C).
Season the beef generously with salt and pepper on all sides.
Sear the Beef:
Heat the oil in a large Dutch oven over medium-high heat.
Sear the beef on all sides until a deep golden-brown crust forms, about 3-4 minutes per side. Remove and set aside.
Sauté Vegetables:
In the same pot, add the onions and cook until softened, about 3 minutes.
Add the garlic and cook for another minute, until fragrant.
Build the Flavor:
Stir in the tomato paste and cook for 1-2 minutes to deepen the flavor.
Pour in the red wine (if using) and scrape up any browned bits from the bottom of the pot.
Add the beef broth, Worcestershire sauce, rosemary, thyme, and bay leaves. Stir to combine.
Add Vegetables and Roast:
Return the beef to the pot, nestling it into the liquid. Add the carrots and potatoes around the beef.
Cover the pot with a lid and transfer it to the oven. Roast for 3-4 hours, or until the beef is fork-tender and easily shredded.
Make the Gravy (Optional):
Remove the pot from the oven and transfer the beef and vegetables to a serving platter.
Skim off excess fat from the cooking liquid.
Bring the liquid to a simmer on the stovetop and whisk in the cornstarch slurry. Simmer until thickened to your liking.
Serve:
Slice or shred the beef and serve with the vegetables and gravy on the side.