Slow Cooker Au Gratin Potatoes Recipe

Au gratin potatoes are the ultimate rich, umami-heavy accompaniment to a nice, juicy steak. Come to think of it, there are few, if any, proteins we can imagine wouldn't taste divine with a side of au gratin potatoes. Think about it: scallops, roast chicken, Impossible sausage with au gratin potatoes? If only you had the time to sit around for 90 minutes while your stove works its magic, you could swimming in au gratin potatoes on a daily basis. But wait! We've got a solution. Bake It With Love's Angela Latimer has devised a way to use a slow cooker to make au gratin potatoes!

Since Latimer's recipe involves a slow cooker, the cooking time, will, of course, be longer than if you were using your oven. But the beauty of a slow cooker is it allows you to set it and forget it — in this case for three hours, although it might take as much as another hour for the potatoes to cook all the way through to tender perfection. That being said, when it comes out of the slow cooker, you'll have potatoes au gratin for eight, which you can justifiably claim took four hours to make, though the fact is you'll have spent about 15 minutes of active time, total. Not bad, eh? 

After you've rinsed your potatoes and cut off any visible shoots, the next obvious question is, as Angela Latimer puts it, "To peel or not to peel?" Latimer's answer is that it's totally up to you. "It's totally a personal preference!" What is more important — because it affects cooking evenness — is that your potato slices be uniform in thickness. "The slices should be about an eighth of an inch in thickness," Latimer said.

Latimer likes to do this kind of precision cutting using a mandoline. If you have a mandoline, and you've used it before, then what else is there to say except "get slicing"? If you've never used a mandoline before, Latimer points out that it is absolutely necessary to use the hand protector/guide shown in the photo, one of which should come with your mandoline. A cut resistant glove can offer another layer of protection, but not everyone bothers. Ultimately, Latimer suggests that if this is your first time using a mandoline, then do read the manufacturer's instructions carefully. 

If you don't have a mandoline, a food processor with an ⅛-inch slicing blade is fine. And if you decide to use a chef's knife, Latimer recommends slicing each potato in half lengthwise, then cutting those into half-moon slices. 

In order to transform those sautéed onions you just made into your the gratin sauce for your potatoes, you will need to add the flour. Do so all at once, and then whisk until all of the flour is moistened. It's okay if it's clumpy. Then gradually whisk the milk into the flour and onion mixture, adding one third of the milk at a time. Whisk until the milk is fully incorporated, and then add the garlic, salt, and pepper, and continue cooking, whisking occasionally, until the sauce begins to thicken. Then remove the saucepan from the heat.

Now is the time to place your thin potato slices in the slow cooker pot, which you've already coated with cooking oil or spray. Latimer's recommendation is to arrange the slices in three layers, as follows: Add a first layer, and then add a couple of turns of freshly ground pepper on top. Then add another layer, and more freshly ground pepper. And finally, add a third layer, and another couple of turns of freshly ground pepper.