01 - Preheat oven to 375°F. Lightly grease a large casserole dish.
02 - Heat olive oil in a skillet over medium heat. Cook chopped onion until softened, about 3 minutes. Add minced garlic and cook for an additional minute.
03 - Add ground beef to the skillet along with salt, black pepper, paprika, and dried thyme. Cook until beef is browned, breaking up any clumps. Drain excess fat if needed.
04 - Stir in beef stock and simmer for 5 minutes to meld flavors. Remove from heat.
05 - Arrange half of the sliced potatoes evenly in the bottom of the casserole dish. Spread the seasoned beef mixture over the potatoes, then dollop sour cream on top, spreading lightly.
06 - Place the remaining potato slices over the beef mixture. Pour milk evenly over the casserole. Cover tightly with aluminum foil.
07 - Bake in the preheated oven for 40 minutes.
08 - Remove foil from casserole. Sprinkle shredded cheddar cheese on top and bake uncovered for an additional 15 to 20 minutes, until cheese is golden and potatoes are tender.
09 - Allow casserole to rest for 10 minutes before serving. Garnish with chopped fresh parsley if desired.