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Just potatoes, onions, and butter — layered in the Slow Cooker and left alone all day. By dinner, the whole house smells incredible and you’ve got something rich, golden, and genuinely satisfying with almost no effort at all.
Why You’ll Love It
Only 3 ingredients — potatoes, onions, butter. That’s it, nothing fancy required.
The Slow Cooker does all the work — layer it in the morning, walk away, come home to dinner.
The onions melt into something magical — low, slow heat turns them sweet and silky in a way stovetop just can’t match.
Deeply filling — hearty enough to stand alone with bread, or stretch into a full meal with a fried egg or leftovers alongside.
Leftovers are arguably better — press them in a skillet the next morning and you’ve got crispy potato cakes without trying.
A Few Notes on the Ingredients
Potatoes: I’ve made this with russets, Yukon Golds, and red potatoes. Yukons are my preference — they have this natural buttery quality that plays so well with the actual butter. Russets go a little softer and mushier, which my husband prefers, so sometimes I do half and half to keep the peace. Red potatoes hold their shape more and give you a firmer, chewier bite. I don’t like them as much in this particular dish but I know people who swear by them.
Slice thin. As thin as you can manage without losing a finger. About an eighth of an inch. I do mine by hand because I’ve never actually gotten the hang of a mandoline — I bought one once, used it twice, gave it to my daughter when she got her own apartment. If you have one and know how to use it, this is the time.
Onions: Yellow onions. That’s my answer. They caramelize properly, they don’t get aggressive. Sweet onions work too and if you want a mellower flavor that’s a reasonable swap. I’ve done half yellow, half sweet when that’s what I had on hand and it was lovely, maybe even better — though I keep forgetting to do it on purpose.
Butter: Salted. Always salted in this house. I know some people have opinions about that but I’m not interested in their opinions.
Ingredients
3 tablespoons salted butter, melted — maybe a little more, I’m not going to judge you
2 pounds russet or Yukon Gold potatoes, sliced thin (about ⅛ inch)
2 large yellow onions, sliced thin (⅛ to ¼ inch — I go thinner on the potatoes, a little thicker on the onions)
Salt and pepper if you use them — optional, this works without
How to Make It
Start by buttering the inside of your Slow Cooker. Just rub a little of the melted butter around with a paper towel or your fingers, get the bottom and a bit up the sides. This isn’t just about sticking — it adds flavor to the bottom layer and I think it matters.
Slice everything first and have it ready before you start layering. I tried to do this in stages once, slice a few, layer a few, and it was a mess. My hands were wet, I kept losing track of where I was. Do the slicing, put the potatoes in one Bowl, the onions in another, then you’re organized.
Layer it like you’re shingling a roof. Potatoes first, overlapping slightly, covering the whole bottom. Then a loose handful of onions scattered over the top. Then a drizzle of butter — maybe a teaspoon, maybe a little more. If you salt and pepper your food, a small pinch here. Then repeat. Potatoes, onions, butter. Keep going until you run out of things. The top layer should end with a good drizzle of butter so it gets a little glossy as it cooks.
Lid on, LOW for six to seven hours. I almost always do LOW. I’ve done HIGH at three to four hours when I forgot to start it in the morning, and it works, but the edges don’t get quite as caramelized and the onions stay a little more… present. You want them to disappear, if that makes sense.
When it’s done, take the lid off and let it sit for about ten minutes. This is important and I used to skip it because I was impatient and then I’d wonder why the juices were thin. The rest lets everything settle and thicken a little. The bottom layer will be deeply golden, almost crispy in spots. That’s the best part. Don’t stir it up before you serve it.
Scoop down through all the layers when you dish it out. You want potato and onion in every bite, not just the top. Spoon some of the buttery liquid from the bottom over each bowl.
Variations — What I’ve Tried
A layer of thinly sliced garlic tucked in with the onions is really good — I’ll admit I originally wrinkled my nose at this because the whole point to me is the simplicity of three ingredients, but I tried it and went back for seconds. Not officially endorsing the addition, but not pretending otherwise either.
I’ve tried adding a bit of chicken broth to the bottom of the pot to keep things moist. Don’t bother. The potatoes and onions release plenty of liquid on their own and adding broth just dilutes that lovely concentrated flavor. Learned that the hard way.
If you want this to go further — feed five or six people instead of four — don’t try to cram more potatoes in. Just serve it over thick slices of toasted bread. The bread soaks up the juices and suddenly the whole thing stretches in a way that feels generous instead of sparse.
Leftovers
This reheats beautifully in a skillet. Melt a little butter, put the leftovers in, press them down, leave them alone for a few minutes. The bottom gets crispy and you’ve basically made potato cakes. I’ve eaten this for breakfast with a fried egg on top and felt like I was living my best life, which is a weird thing to feel about cold potato leftovers reheated in a pan, but here we are.
It keeps in the fridge for three or four days. I’ve pushed it to five and it was fine, a little wetter, but fine. The potatoes start to absorb more of the butter as it sits, which I actually like. The flavor deepens.