Preheat your oven to 300 degrees F. This low and slow method will ensure that the meat becomes tender and flavorful.
Rinse the brisket and pat it dry. This helps season the meat more effectively. Rub both sides of the brisket with black pepper and kosher salt, ensuring it's evenly coated.
In a large roasting pan, heat over medium flame on the stovetop. Drizzle in a few tablespoons of olive oil, and once hot, add the brisket. Brown it on both sides, which should take about 4 minutes per side. This step creates a lovely crust and enhances flavor.
Once browned, carefully remove the brisket from the pan. Drizzle a little more olive oil in the pan, then add the diced onions, carrots, and celery chunks. Sauté them for a few minutes until the onions are translucent and carrots are slightly caramelized, scraping up the brown bits from the bottom of the pan.
After the vegetables are sautéed, scoop them out into a bowl. Next, pour enough beef broth into the pan to cover the bottom, scraping up any remaining brown bits as the broth heats.
Once the broth is hot, add half of your sautéed vegetables back into the pan, spreading them out evenly. Carefully place the brisket back into the pan, ensuring the fatty side is facing up. Top with garlic cloves and the remaining sautéed vegetables. Then, scatter the thyme, rosemary, and bay leaves on top.
Pour additional broth into the pan until it reaches halfway up the sides of your brisket. Cover the roasting pan tightly with parchment paper and foil, or use a lid if your pan has one.
Let the brisket roast undisturbed for 5 to 7 hours. The cooking time may vary depending on the size and type of brisket. It's ready when it's fork-tender and easy to slice.
Once cooked, carefully remove the brisket from the pan and allow it to rest on a cutting board for 20 to 30 minutes before slicing. This resting period makes slicing easier and helps retain moisture.
While the brisket is resting, strain the pan drippings into a saucepan and let it cool slightly. Skim off the fat from the surface with a spoon. Reheat the drippings, then mix potato starch with cold water and stir into the liquid, bringing it to a simmer until it thickens into a gravy. You can also blend the softened vegetables into the gravy for added texture.
After resting, slice the brisket thinly against the grain. Serve it topped with the gravy and any reserved vegetables, garnishing with fresh parsley if desired.
For make-ahead options, let the brisket return to room temperature, transfer it to a ceramic dish, cover it, and refrigerate. When ready to serve, reheat in a preheated oven until warmed through.
