Preheat your oven to 300°F (150°C).

Pat the beef brisket dry with paper towels. Season generously with salt and black pepper on both sides.

In a large Dutch oven or heavy oven-safe pot, heat the olive oil over medium-high heat. Add the brisket and sear for about 4-5 minutes on each side until browned. Remove the brisket from the pot and set aside.

In the same pot, add the diced onion and minced garlic. Sauté for about 3-4 minutes until the onion is translucent.

Stir in the beef broth, red currant jelly, balsamic vinegar, Worcestershire sauce, thyme, rosemary, and bay leaf. Bring the mixture to a simmer.

Return the brisket to the pot, making sure it is submerged in the liquid. Cover the pot with a lid and transfer it to the preheated oven. Braise for about 3 to 4 hours, or until the brisket is tender and easily pulls apart with a fork.

Once the brisket is done, remove it from the pot and cover it with foil to keep warm. Strain the braising liquid through a fine-mesh sieve into a saucepan. Discard the solids. If you prefer a thicker gravy, mix the cornstarch with a little cold water to make a slurry, then add it to the saucepan. Simmer the sauce over medium heat until it thickens.

Slice the brisket against the grain and serve it drizzled with the velvety herb pan gravy. Garnish with fresh parsley.