Preheat your oven to 300°F (150°C).

In a large Dutch oven, heat the olive oil over medium-high heat. Season the brisket generously with salt and pepper. Sear the brisket on both sides until browned, about 5-7 minutes per side. Remove the brisket and set aside.

In the same pot, add the sliced onions and whole garlic cloves. Sauté for about 5 minutes until the onions are translucent.

Stir in the chopped quince and cook for an additional 3-4 minutes until slightly softened.

If using, pour in the red wine to deglaze the pot, scraping up any brown bits from the bottom. Bring to a simmer and cook for 2-3 minutes.

Add the beef bone broth, balsamic vinegar, brown sugar, thyme, and rosemary. Stir to combine.

Return the brisket to the pot, making sure it is submerged in the liquid. Bring to a gentle simmer, cover the pot, and transfer it to the oven.

Braise the brisket in the oven for 3-4 hours, or until the meat is fork-tender.

Once cooked, remove the brisket from the oven and let it rest for 15-20 minutes before slicing.

While the brisket rests, strain the cooking liquid into a saucepan. Simmer on medium heat to reduce slightly and thicken into a gravy. Adjust seasoning with salt and pepper as needed.

Slice the brisket against the grain and serve with the rich bone broth gravy drizzled on top. Garnish with fresh parsley.