Preheat your oven to 375°F (190°C).
Cook ground beef in a skillet until browned; drain excess fat.
Add onions and garlic to the skillet; cook until soft and fragrant.
In a bowl, mix cream of mushroom soup with milk, salt, and pepper.
Layer half the potatoes in a greased casserole dish; top with half of the beef mixture and half the cheese.
Repeat layers and finish with the remaining cheese.
Pour soup mixture over the layers evenly.
Cover the casserole with foil and bake for 45 minutes.
Remove foil and bake for an additional 15 minutes, until bubbly and golden brown.
Let cool slightly, garnish with parsley, and serve warm.