For the rub: In a small bowl, mix together the rosemary, thyme, oil, salt, and pepper until smooth.
Preheat the oven to 350 degrees F. Pat the beef dry with paper towels and rub on all sides with the herb rub. In a heavy 6-quart pot or Dutch oven, heat 2 tablespoons of oil over medium-high heat. Add the beef and cook until browned on all sides, about 12 minutes. Remove the beef and set aside.
Add the remaining oil, onions, carrots, and fennel to the pot. Season with salt and pepper. Cook, stirring frequently, until tender, about 8 minutes. Add the garlic and cook for 1 minute until aromatic. Add the sherry and scrape up the brown bits that cling to the bottom of the pan with a wooden spoon. Stir in the broth and bay leaves. Return the beef and any juices to the pot and bring the liquids to a boil. Cover the pot and transfer to the oven. Cook until the beef is fork-tender, about 4 hours, turning the beef over halfway through and adding extra broth, as needed, to keep the beef halfway covered in liquid.
Transfer the beef to a cutting board. Tent with foil and let stand for 15 minutes. Spoon any excess fat off the top of the pan juices. Remove the bay leaves and discard. Using an immersion blender, blend the vegetables and cooking juices together until smooth. (The vegetables can also be pureed in a blender). Season with salt and pepper, to taste. Keep warm over low heat.
Cut the beef into 1-inch pieces and place on a platter. Spoon some of the sauce over the meat and serve the remaining sauce on the side.