Preheat your oven to 375°F (190°C), and grease a 9x13-inch baking dish with butter or cooking spray.

In a large skillet over medium heat, cook the ground beef for 6-8 minutes until browned. Drain excess fat, then add onions and garlic, sautéing for 2-3 minutes.

Reduce heat to low, stir in the cream of mushroom soup and milk until combined and creamy, then remove from heat.

Wash and peel potatoes if desired, then slice into thin rounds (about 1/8 inch thick).

Layer sliced potatoes at the bottom of the baking dish, then spoon half the beef mixture over the potatoes and sprinkle with cheese. Repeat layers.

Cover with aluminum foil and bake for 60 minutes. Remove foil and bake for an additional 15-20 minutes until golden and bubbly.