Preheat Oven and Prepare Vegetables

Preheat your oven to 350°F (175°C).

Peel and thinly slice the 4 russet potatoes. A mandoline is helpful for uniform slices.

Chop the onion and set both aside.

Brown the Beef

Heat 1 tablespoon olive oil in a skillet over medium heat.

Add the chopped onion and cook for about 3 minutes until softened.

Add the ground beef and cook until browned, about 6–8 minutes.

Drain excess grease, then season the mixture with garlic powder, paprika, salt, and pepper.

Prepare the Sauce

In a separate bowl, whisk together the condensed cream of mushroom soup and ¾ cup milk until smooth.

Layer the Casserole

Lightly grease a 9×13-inch baking dish with the remaining olive oil.

Arrange half of the sliced potatoes in a flat layer on the bottom.

Top with half of the ground beef mixture.

Pour half of the soup mixture over the beef and potatoes.

Sprinkle with 1 cup of shredded cheddar cheese.

Repeat with the remaining potatoes, beef, soup mixture, and cheese.

Bake

Cover the baking dish tightly with aluminum foil.

Bake in the preheated oven for 1 hour.

Remove the foil and bake for an additional 30 minutes, or until the potatoes are tender and the cheese is golden and bubbly.

Garnish and Serve

Remove from the oven and let the casserole rest for 5–10 minutes.

Garnish with chopped fresh parsley and serve hot.