Preheat your oven to 325°F (163°C).

Prepare the garlic by cutting the top off the head, exposing the individual cloves. Drizzle with olive oil, wrap in foil, and roast in the oven for about 30-40 minutes, or until soft and fragrant. Allow to cool slightly, then squeeze the cloves out of their skins into a bowl and mash.

Season the beef brisket generously with salt and black pepper on both sides. In a large, heavy-bottomed Dutch oven, heat the remaining olive oil over medium-high heat. Add the brisket and sear on all sides until browned, about 4-5 minutes per side. Remove the brisket and set aside.

In the same pot, add the blackberries, beef broth, red wine, balsamic vinegar, brown sugar, mashed roasted garlic, thyme, rosemary, and bay leaf. Stir to combine and bring to a simmer.

Return the brisket to the pot, cover, and transfer 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 done, remove the brisket from the pot and let it rest for 15-20 minutes before slicing.

If desired, to make a thicker gravy, strain the braising liquid into a saucepan and bring to a simmer. Mix cornstarch with a bit of water to create a slurry, then whisk it into the simmering liquid until thickened to your liking.

Serve the sliced brisket drizzled with the herb pan gravy. Garnish with fresh herbs before serving.