Preheat the oven to 325°F (163°C).

In a large Dutch oven, heat olive oil over medium-high heat. Season the brisket with salt and pepper. Sear the brisket on both sides until browned, about 4-5 minutes per side. Remove the brisket and set aside.

In the same pot, add the diced onion and sauté until softened, about 3-4 minutes. Stir in the roasted garlic and cook for an additional minute.

Add the wild blackberries, beef broth, red wine, balsamic vinegar, brown sugar, Worcestershire sauce, thyme, and rosemary to the pot. Stir to combine and bring the mixture to a simmer.

Return the brisket to the pot, ensuring it is submerged in the liquid. Cover the pot with a lid and transfer it to the preheated oven.

Braise the brisket in the oven for 3 to 4 hours, or until the meat is tender and easily pulls apart with a fork.

Once cooked, remove the brisket from the pot and transfer it to a cutting board. Let it rest for 10-15 minutes before slicing against the grain.

Meanwhile, strain the braising liquid into a saucepan to remove the solids. Bring the liquid to a boil over medium-high heat and reduce it until thickened, about 10-15 minutes. Season with salt and pepper to taste.

Serve the sliced brisket drizzled with the velvety bone broth gravy and garnish with fresh blackberries and thyme sprigs.