Preheat your oven to 375°F (190°C) and grease a 9×13-inch baking dish with cooking spray or olive oil.
Heat olive oil in a large skillet over medium heat. Add the ground beef and cook, breaking it apart with a spoon, until browned and fully cooked (about 5-7 minutes). Drain any excess fat if necessary.
Add the chopped onion and minced garlic to the skillet with the beef. Cook for another 3-4 minutes, or until the onion becomes soft and translucent.
Spread the cooked ground beef mixture evenly across the bottom of the prepared baking dish.
Layer the thinly sliced potatoes over the ground beef. Season the potatoes with salt, pepper, and half of the Italian seasoning and paprika.
Sprinkle the shredded cheddar cheese and grated Parmesan cheese evenly over the potatoes.
Pour the beef broth (or water) around the edges of the casserole to keep the potatoes moist while baking. Optionally, drizzle with milk for added creaminess.
Cover the dish with aluminum foil and bake for 30 minutes.
After 30 minutes, remove the foil and bake for an additional 15-20 minutes, or until the potatoes are tender and the cheese is bubbly and golden.
Garnish with fresh parsley if desired and serve hot.
Notes
For a leaner dish, brown the ground beef thoroughly and drain any excess fat.
The ketchup and milk are optional but can add extra flavor and creaminess to the casserole.