Grandma swore by this little trick for Sunday dinner. I couldn't believe how filling it was with just 4 ingredients. The smell alone makes people wander into the kitchen.

This 4-ingredient scalloped potato dish is the kind of thing my grandma would pull out for Sunday dinner when money was tight but company was plenty. She always said her little trick was to let simple ingredients do the work: thinly sliced potatoes, real cream, a good handful of cheese, and just enough onion to perfume the whole house. No fancy sauces, no long list of seasonings—yet the pan would come out of the oven bubbling and golden, and folks would start wandering into the kitchen just from the smell. It’s rooted in old Midwestern farmhouse cooking, where a bag of potatoes and some dairy from the barn had to stretch to feed a crowd. This version stays true to that spirit: humble, hearty, and surprisingly filling for how little goes into it.

Serve these scalloped potatoes piping hot right out of the glass casserole dish, with a big spoon so everyone can dig into those creamy, browned edges. They’re lovely alongside a simple Sunday roast, baked ham, or meatloaf, but they also hold their own with nothing more than a green salad or a dish of buttered peas. If you’re feeding a crowd, add some crusty bread to mop up the creamy sauce and a tangy coleslaw to balance the richness. Leftovers reheat nicely and make a fine partner to scrambled eggs or a slice of leftover roast for an easy next-day meal.

Servings: 6

3 pounds russet or Yukon Gold potatoes, peeled and very thinly sliced

Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch glass casserole dish with a bit of butter or oil if you like, but it’s not counted as one of the four ingredients.

Grandma’s little trick is in the slicing: using a sharp knife or mandoline, slice the potatoes as thinly and evenly as you can, about 1/8 inch thick. Do the same with the onion. The thin, even slices help the potatoes cook through and create their own silky sauce with the cream and cheese.

Pat the sliced potatoes dry with a clean kitchen towel or paper towels to remove excess moisture. This helps the cream cling to the potatoes and encourages a richer, thicker sauce instead of a watery one.

Layer about one-third of the potatoes in the bottom of the prepared glass dish, spreading them into an even layer and fanning them slightly. Scatter one-third of the sliced onion over the potatoes, then sprinkle with about one-third of the shredded cheddar.

Repeat the layering two more times: potatoes, onion, then cheese, finishing with a generous layer of cheese on top. This stacked layering is what gives you those tender, creamy layers underneath and the golden, crispy top that everyone fights over.

Slowly pour the heavy cream evenly over the entire dish, letting it seep down between the layers. Gently jiggle the dish or tap it on the counter so the cream settles in around the potatoes.

Cover the casserole tightly with foil and place it on the middle rack of the preheated oven. Bake covered for 45 minutes, until the potatoes are starting to soften and the cream is bubbling around the edges.

Remove the foil and continue baking, uncovered, for 25–35 minutes more, or until the top is deeply golden brown, the cream is thick and bubbly, and a knife slips easily through the center of the potatoes. The uncovered time is when that browned, crisp-cheesy top forms.

Once done, carefully remove the dish from the oven and let the potatoes rest for at least 10–15 minutes before serving. This rest time lets the creamy sauce thicken and the layers settle so you can scoop out neat, hearty servings without everything sliding apart.

Serve warm, scooping down to the bottom so everyone gets a bit of the tender potatoes, sweet onion, creamy sauce, and crispy golden top in each spoonful.

If you’d like a little more depth without adding more main ingredients, you can grind a bit of black pepper or sprinkle a light pinch of salt between layers, but the cheese usually brings enough saltiness on its own. For a slightly lighter version, you can swap half of the heavy cream for whole milk; just know the sauce will be a bit less rich and not quite as thick. If you prefer a stronger onion flavor, use a large onion instead of a medium, or tuck a few of the onion slices right along the sides of the dish so they caramelize against the glass. For a smokier taste, use smoked cheddar or a blend of cheddar and another melty cheese, keeping the total amount at about 2 cups so the dish still bakes properly. To make ahead, assemble the casserole, cover tightly, and refrigerate up to 24 hours; add 5–10 minutes to the baking time if it goes into the oven cold. Food safety tips: Keep the heavy cream refrigerated until you’re ready to assemble, and don’t leave the baked potatoes at room temperature for more than 2 hours. Cool leftovers promptly, cover, and refrigerate; they’re best eaten within 3–4 days. Reheat leftovers in a 325°F (165°C) oven, covered with foil, until hot in the center, which helps bring back that creamy texture and keeps the top from burning.