Heat oil in a large, heavy pot (such as a Dutch oven) over high heat. Add the beef, season generously with salt and black pepper, and break it apart as you would when browning ground meat. Let it cook undisturbed for 2 minutes to develop a deep sear, then stir occasionally until fully cooked, about 7 minutes.
If the pot is dry (this will depend on how lean your beef is), add a glug of oil to it. Add the onion and mushrooms, season with a large pinch of salt and a little more pepper, and cook, stirring now and then until softened a bit and browned in spots, about 10 minutes. Add the Worcestershire sauce and garlic and cook until very fragrant, about 30 seconds.
Stir in the rice and broth. Bring the mixture to a boil, then immediately lower the heat so that the mixture simmers. Season the cooking liquid to taste with salt (the exact amount will depend on how salty your broth is), cover the pot, and cook until the rice is tender, about 25 minutes. Remove the pot from the heat and let the rice sit, covered, for 10 minutes.
Uncover the pot, add the cheese, give everything a good stir, and serve immediately.
