Step 1 of 13
Oven-Braised Beef Brisket
Lay the brisket on a clean work surface or cutting board. Using the tip of a knife, cut small slits over the surface of the fatty side. Season the brisket liberally with the salt and pepper. Let the meat stand for 30 minutes at room temperature.
Step 2 of 13
Oven-Braised Beef Brisket
Meanwhile, peel the onion and carrots. Slice the onion into 3/4-inch half-moons, and slice the carrots on a diagonal into 1-inch pieces. Peel and smash the garlic cloves.
Step 3 of 13
Oven-Braised Beef Brisket
Preheat the oven to 300°F.
Step 4 of 13
Oven-Braised Beef Brisket
Set a large Dutch oven over medium-high heat and add the oil. When oil is shimmering, carefully place the brisket, fat side down, into the pot. Sear without moving until deeply browned on the bottom, 3-4 minutes. Flip brisket and sear on the opposite side, 3-4 minutes.
Step 5 of 13
Oven-Braised Beef Brisket
Transfer the brisket to a large platter.
Step 6 of 13
Oven-Braised Beef Brisket
Reduce heat under Dutch oven to medium. Add the onion, carrots, garlic, and herbs. Cook, stirring occasionally, until onion is slightly softened, 4-5 minutes. Pour the beef broth into the pot, scraping up any browned bits from the bottom. Stir in the vinegar and ketchup.
Step 7 of 13
Oven-Braised Beef Brisket
Set brisket, fat side up, on top of vegetables. Pour any drippings from the platter into pot. Bring liquid to a simmer, then remove pot from heat. Cover the Dutch oven with a lid (the lid needs to fit very snugly; if it doesn't, first tightly cover pot with a piece of foil).
Step 8 of 13
Oven-Braised Beef Brisket
Bake the brisket on middle rack of oven until tender when pierced with a fork, about 4 hours.
Step 9 of 13
Oven-Braised Beef Brisket
Check to see that brisket is done. Remove from oven or add time as needed.
Step 10 of 13
Oven-Braised Beef Brisket
Transfer the meat to a cutting board and tent loosely with foil.
Step 11 of 13
Oven-Braised Beef Brisket
Strain the liquid from the Dutch oven through a colander into a large bowl. Set the vegetables aside. Measure the liquid; you should have about 2 cups. Add beef broth if needed (or if you have too much liquid, save it for another use).
Step 12 of 13
Oven-Braised Beef Brisket
Pour 1/4 cup of the strained liquid into a medium saucepan. Add the cornstarch and whisk until the mixture is completely smooth. Stream the remaining liquid into the saucepan and whisk to combine. Set over medium heat and cook, whisking steadily, until sauce bubbles and thickens, 2-4 minutes. Transfer to a gravy boat or serving bowl.
Step 13 of 13
Oven-Braised Beef Brisket
Cut the brisket into wide slices and transfer to a serving platter. Discard the herb stems and bay leaf from the carrots and onions, then spoon vegetables around the meat. Scatter the fresh thyme leaves over the meat and carrots and tuck in thyme sprigs. Serve with the gravy.