Preheat your oven to 350°F (175°C).

In a large skillet over medium heat, add the ground beef, breaking it apart into small crumbles. Cook for about 7-10 minutes or until no longer pink, then drain excess fat.

Add the finely chopped onion to the skillet with the browned beef and sauté for another 3-4 minutes until translucent.

In a large bowl, mix the beef and onion combination with the cream of mushroom soup and milk until well-combined.

Layer half of the sliced potatoes on the bottom of a greased baking dish.

Spoon half of the beef mixture over the potatoes, spreading it evenly.

Repeat the process with the remaining potatoes and beef mixture.

Sprinkle the shredded cheese over the top layer.

Cover with aluminum foil and bake for 30 minutes, then remove foil and bake uncovered for an additional 15 minutes until cheese is bubbly.

Let it cool for about 5-10 minutes before serving.