Preheat the oven to 300 degrees . In a large bowl, combine the beef, 1 tablespoon oil, garlic and rosemary. Season with salt and pepper.
In a large, heavy saucepan, heat the remaining 2 tablespoons oil over medium heat and sear the beef in batches, turning the pieces to brown on all sides; transfer to a plate. Add the onion to the pot and cook until slightly softened, about 2 minutes.
In a large casserole dish, combine the beef and onion with the turnip, carrots, parsnips, tomatoes and bay leaves; season with salt and pepper. Add the broth and wine to the saucepan and bring to a boil, scraping up the browned bits from the bottom of the pan. Pour the hot liquid over the meat and vegetables. Cover with foil and bake until the beef is tender, about 2 hours.
Meanwhile, in a large pot of salted water, bring the potatoes to a boil and cook until tender, about 15 minutes. Drain and mash with the cream and butter; season with salt and pepper.
Preheat the broiler. Spoon off about 1-1/2 cups liquid from the casserole and set aside; discard the bay leaves. Spread the mashed potatoes over the meat and broil until golden. Reheat the reserved meat juices (discarding the surface fat), and serve alongside.