Preheat your oven to 325°F (163°C).

In a large skillet, heat 1 tablespoon of olive oil over medium-high heat. Add the leeks, cut side down, and sear until they are nicely browned, about 5-7 minutes. Remove and set aside.

In a small bowl, combine the minced garlic, smoked marjoram, thyme, sea salt, and black pepper. Rub this mixture all over the beef chuck roast.

In the same skillet, add the remaining tablespoon of olive oil and sear the beef roast on all sides until browned, about 3-4 minutes per side.

In a large roasting pan, place the seared roast in the center. Arrange the fire-roasted leeks around the roast.

In a bowl, whisk together the beef broth and balsamic vinegar. Pour the mixture over the roast and leeks.

Cover the roasting pan with aluminum foil and place it in the preheated oven. Roast for 3-4 hours, or until the beef is tender and easily pulls apart with a fork.

Once done, remove the roast from the oven and let it rest for 15 minutes before slicing.

While the roast is resting, pour the cooking liquid into a saucepan over medium heat. Bring to a simmer, then whisk in the butter until melted and the gravy is velvety.

Slice the beef and serve it warm with the fire-roasted leeks and balsamic gravy. Garnish with fresh parsley.