1. Preheat your oven to 375°F (190°C) and gather all your ingredients to ensure a smooth cooking process.
2. Heat a large skillet over medium-high heat and cook ground beef with chopped onion and minced garlic. Stir frequently until the beef is browned and the onions are translucent, about 7–10 minutes. Drain excess fat and set the mixture aside.
3. Slice Russet or Yukon Gold potatoes into thin rounds or cubes, approximately 1/4 inch thick, ensuring even cooking. Peel the potatoes if desired, or leave the skin on for a rustic touch.
4. Grease a baking dish and begin layering the casserole. Add a layer of potatoes, followed by a portion of the cooked ground beef mixture. Sprinkle a combination of mozzarella and sharp cheddar cheese over the beef. Repeat the layers, finishing with a cheese layer on top.
5. In a saucepan, melt butter over medium heat. Gradually whisk in flour to create a smooth paste. Slowly add milk and beef broth while stirring continuously. Once thickened, whisk in Greek yogurt and seasonings like garlic powder, onion powder, paprika, salt, and pepper.
6. Pour the prepared creamy sauce evenly over the layered ingredients in the baking dish. Ensure the sauce seeps through all layers for a rich, well-combined flavor.
7. Cover the baking dish with aluminum foil and bake in the preheated oven for 45 minutes to 1 hour. This helps the potatoes become tender and melds the flavors together.
8. Remove the foil and increase the oven temperature to 400°F (200°C). Bake uncovered for an additional 15–20 minutes, allowing the cheese topping to turn golden brown and bubbly.
9. Let the casserole rest for a few minutes after baking to set and make it easier to portion.
10. Serve the Easy Hamburger Potato Casserole as a hearty main dish, optionally paired with a fresh salad or steamed vegetables for a complete meal. Enjoy!