Preheat the oven to 375°F (190°C).
Cut the cauliflower into florets and steam until tender, about 10 minutes.
While cauliflower steams, heat olive oil in a skillet over medium heat.
Add diced onion and garlic, cooking until soft and fragrant.
Add ground beef to the skillet, breaking it up as it cooks.
Stir in beef broth, thyme, Worcestershire sauce, salt, and pepper.
Let the beef mixture simmer until slightly thickened, about 5 minutes.
Drain cauliflower and mash with butter until smooth and creamy.
Transfer beef mixture to a baking dish, spreading evenly.
Top with cauliflower mash and sprinkle with cheese if using.
Bake for 20 minutes, until the top is golden and bubbly.
Serve hot and enjoy the low-carb comfort!