Preheat Oven & Prep Dish
Heat oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish with nonstick spray.
Cook the Beef & Onion
In a large skillet, cook the ground beef and diced onion over medium-high heat until the meat is browned and onions are tender. Drain excess fat and set aside.
Slice the Potatoes
Peel and slice the potatoes into even ¼-inch thick rounds for consistent cooking.
Assemble the Layers
In your prepared baking dish, layer the ingredients as follows:
A layer of sliced potatoes
A sprinkle of salt and pepper
A portion of the cooked beef and onion mixture
A handful of shredded cheddar
Repeat these layers until all ingredients are used, finishing with a generous cheese layer on top.
Make the Sauce
In a mixing bowl, whisk together the cheddar cheese soup, evaporated milk, and regular milk until smooth. Season with additional salt and pepper if desired.
Add Sauce & Bake Covered
Pour the sauce evenly over the casserole, allowing it to seep through the layers. Cover tightly with foil and bake for 60 minutes.
Uncover & Finish Baking
Remove the foil and bake for an additional 15 minutes, or until the top is golden and bubbly. If your potatoes were sliced thicker, extend the covered bake time as needed.
Rest & Serve
Let the dish rest for 5–10 minutes before serving to help everything set.
