My sister-in-law begged me for this one after the graduation party. Creamy, buttery, and not a single leftover.

This 4-ingredient slow cooker potato gratin is exactly the kind of dish that disappears at a graduation party or backyard cookout—creamy, buttery, and rich enough that people go back for seconds. It’s built on thin-sliced Idaho potatoes, which hold their shape beautifully while turning tender and velvety in a slow cooker. I lean on heavy cream, butter, and a little salt to do the heavy lifting here; no flour, no extra fuss. It’s a practical, set-it-and-forget-it approach that frees up your oven for everything else on a busy celebration day, but still feels like something you’d happily serve to family you want to impress. My sister-in-law did, in fact, beg for this recipe after our last graduation party—there wasn’t a spoonful left in the crock.

Serve this creamy slow cooker gratin straight from the crock on a warm setting so the edges stay golden and the center stays silky. It’s perfect alongside grilled steak, chicken, or brats, and it loves simple summer sides like a vinegary coleslaw or a crisp green salad to balance the richness. A platter of sliced tomatoes with a little salt and olive oil or grilled asparagus also works nicely. For a fuller spread, pair it with roasted vegetables and a bright herb sauce or chimichurri—the potatoes soak up those flavors wonderfully.

Servings: 8-10

3 pounds Idaho potatoes, peeled and very thinly sliced (about 1/8 inch)

Prepare the slow cooker: Generously butter the bottom and sides of a 5- to 6-quart oval slow cooker. This helps keep the potatoes from sticking and encourages those golden, crisped edges you want around the sides.

Slice the potatoes: Peel the Idaho potatoes and slice them very thinly, about 1/8 inch thick. A mandoline is helpful for even slices, but a sharp knife works if you take your time. Keep the slices roughly the same thickness so they cook evenly and become tender at the same time.

Mix the cream and butter: In a medium bowl or large measuring cup, whisk together the heavy cream, melted butter, and kosher salt until the salt is mostly dissolved and the mixture looks cohesive. This is your simple, rich sauce that will soak into the potatoes as they cook.

Layer the potatoes: Add a loose, even layer of sliced potatoes to the bottom of the buttered slow cooker, overlapping them slightly like shingles. Drizzle or spoon a small amount of the cream-butter mixture over the layer, just enough to lightly coat the potatoes. Repeat with more layers of potatoes and cream mixture, continuing until you’ve used all the potatoes and sauce. Gently press down on the top layer with your hands or a spatula to settle everything and help the cream work its way between the slices.

Cook on low: Cover the slow cooker with its lid. Cook on LOW for 4 1/2 to 6 hours, or until the potatoes are very tender when pierced with a knife and the edges around the crock are bubbling and golden. Avoid lifting the lid in the first few hours; each peek releases heat and can lengthen the cooking time.

Optional finish for extra browning: If your slow cooker insert is oven-safe and you want deeper browning on top, carefully remove the insert once the potatoes are tender and place it under a preheated broiler for 3 to 5 minutes, watching closely, until the surface is spotty brown. Let it rest a few minutes before moving it back to the slow cooker base (set to WARM) or to the counter.

Rest and serve: Once done, turn the slow cooker to WARM and let the gratin rest, covered, for 15 to 20 minutes. This brief rest helps the cream thicken slightly so the potatoes slice and scoop more cleanly. Taste a small bite and add a pinch more salt at the table if needed. Serve directly from the slow cooker, making sure each scoop has some of the golden, crisped edges and the creamy center.

For a slightly lighter version, you can replace up to 1/2 cup of the heavy cream with whole milk, though the texture will be a bit less luxurious. If you enjoy a subtle garlic note, rub a peeled garlic clove around the buttered slow cooker before layering the potatoes, or add one lightly crushed clove to the cream mixture and remove it before serving. A few grinds of black pepper or a pinch of smoked paprika over the top before cooking will add gentle warmth without changing the spirit of the recipe. For a make-ahead option, you can thinly slice the potatoes up to 4 hours in advance and store them submerged in cold water in the refrigerator; drain and pat dry thoroughly before layering so you don’t dilute the cream. Food safety notes: Always keep the potatoes refrigerated until you’re ready to cook, and don’t leave the finished gratin at room temperature for more than 2 hours—after that, cool and refrigerate leftovers promptly in shallow containers. Reheat leftovers thoroughly until steaming hot in the center (165°F/74°C) before serving. If using the broiler to brown the top, handle the hot slow cooker insert carefully with oven mitts and place it on a heatproof surface to avoid burns or thermal shock.