There’s no easier side dish than roasting potatoes in a hot oven with a sprinkling of olive oil, salt, and pepper. But a technique I tried a few weeks ago, from a recipe by Kenji Lopez-Alt, author of The Food Lab: Better Home Cooking Through Science, led to some of the crispiest and most flavorful potatoes I’ve ever cooked. From now on, I’ll be adding Kenji potatoes to my regular repertoire. 

Lopez-Alt explains that boiling your potatoes first, before roasting them, helps build up a layer of gelatinized starch that makes the exterior extremely crisp. And then, by tossing the parcooked spuds with oil or fat, you rough them up a bit, creating additional craggy surface area that gets extra-crispy during roasting.

Although Lopez-Alt suggests that for the crispiest potatoes, you should toss them in duck fat or an oil with a high saturated fat content, I used olive oil, and they were still spectacular. The exteriors of the potatoes had a thin crispy layer, and the interiors were smooth and creamy. The double-cooking method takes quite a bit longer than traditional roasting – after boiling the potatoes for about 15 minutes, I roasted them for 45 minutes, flipping them at the halfway point – but the results were easily worth the extra effort.

Lopez-Alt’s expertise extends to other potato preparations, of course. On a recent episode of the Special Sauce podcast, host Ed Levine interviewed Lopez-Alt about his tips for the best french fries. And again, double cooking plays a prominent role. Lopez-Alt says that frying your potatoes first at a lower temperature, and then letting them cool before frying them at a higher temperature, also helps build up that layer of gelatinized starch that creates crispiness. The cooling process redistributes the interior moisture that’s left after the first fry, while the second fry draws out more of the moisture, leaving you with a crispy, crunchy exterior and a tender interior.

For the perfect french fries, Lopez-Alt also offers these tips:

• As with roasted potatoes, boiling before the first fry helps gelatinize more starch and will lead to extra-crispy fries
• Adding a tablespoon of white vinegar per quart of water helps ensure that the potatoes will hold their shape
• Using aromatics like peppercorns, garlic, and bay leaves in the boiling water will create an additional layer of flavor
• Fry in vegetable oil with a high level of saturated fat, like peanut oil, or use animal fat like lard, beef fat, or duck fat
• Freezing your potatoes overnight after the first fry will create ice crystals that helps the fries come out even crispier and fluffier after the second fry. (Lopez-Alt says there’s a good reason why store-bought frozen french fries are usually consistently great.)

Now that I’ve mastered the crispy roasted Kenji potatoes, I’m going to have to get my hands on some duck fat so I can try out making homemade french fries. But first, I should probably learn what Lopez-Alt says about how to make a perfect burger. Or maybe a bacon cheeseburger. All this writing about french fries is getting me hungry.

What I Ate: Twice-cooked super-crisp roasted potatoes