Preheat the oven to 375 degrees and lightly grease a 9x13 inch baking dish.
In a large skillet over medium heat, cook the ground beef until browned, breaking it up as it cooks.
Add the diced onion and minced garlic to the skillet and cook for 3 minutes until the onion softens.
Stir in the beef broth, thyme, salt, and black pepper, then simmer for 2 minutes.
Arrange half the sliced potatoes in an even layer in the prepared baking dish.
Spoon the beef mixture over the potatoes, then top with the remaining potato slices.
Cover the dish with foil and bake for 45 minutes.
Remove the foil, sprinkle the cheddar cheese evenly over the top, and bake uncovered for 15 more minutes until the cheese melts and the potatoes are tender.