Preheat the oven to 375°F (190°C).
Heat olive oil in a large skillet over medium heat.
Add diced onion and minced garlic to the skillet and sauté for 3-4 minutes until softened.
Add ground beef to the skillet and cook, breaking it apart with a spoon, until browned and cooked through, about 6-8 minutes.
Season the beef mixture with salt, black pepper, and dried thyme. Stir well and remove from heat.
In a large mixing bowl, combine beef broth and sour cream until smooth.
Lightly grease a 9×13 inch casserole dish.
Arrange half of the sliced potatoes in an even layer on the bottom of the casserole dish.
Spread half of the cooked ground beef mixture evenly over the potatoes.
Pour half of the sour cream and beef broth mixture over the beef layer.
Sprinkle half of the shredded cheddar cheese over the mixture.
Repeat with the remaining potatoes, ground beef mixture, sour cream mixture, and cheddar cheese, creating a second layer.
Cover the casserole dish with aluminum foil and bake in the preheated oven for 30 minutes.
Remove the foil and bake for an additional 15 minutes, or until the potatoes are tender and the cheese is golden and bubbly.
Let the casserole rest for 5 minutes before serving.