The Food Lab: How to Roast the Best Potatoes of Your Life

The Food Lab

Unraveling the mysteries of home cooking through science.

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[Photographs and video: J. Kenji López-Alt]

The Brits get a bad rap for their cuisine, and in some cases rightfully so—the beef cooked until gray and the gravy-made-from-granules that I ate every Sunday while staying in England were not the height of culinary greatness— but dang if there aren't a lot of things they do better than almost anyone else. I'm talking savory pies, fried fish, Yorkshire puddings, and roasted potatoes. The British method of roasting potatoes is one that I've taken a strong liking to. It's simple, and it produces amazing results. Boil chunks of potato until they're just tender, toss them none-too-gently with fat (ideally beef drippings) to rough up their surface, then roast them until they're crisp and crackling.

The boiling and roughing-up steps are the real key. They create a thin slurry of mashed potato that clings to the surface of the potato chunks, which ends up crisping beautifully in the oven as the potatoes roast. It's the technique I use for the Ultra-Crispy Roast Potatoes recipe I published back in 2011, and the technique I use for pretty much every holiday.

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This year, I decided to reexamine the method from the ground up with the idea of completely maximizing that crisp-to-creamy contrast in each chunk of roast potato, testing and retesting every variable, from cut size to potato type to boiling and roasting methods. The result is this recipe, which I firmly and un-humbly believe will deliver the greatest roast potatoes you've ever tasted: incredibly crisp and crunchy on the outside, with centers that are creamy and packed with potato flavor. I dare you to make them and not love them. I double-dare you.

Here's how the testing went down.

Potato Size and Variety

First things first: Let's talk about size. In my original roast-potatoes recipe, I cut the potatoes into smallish, two-inch chunks. This time around, I wanted to maximize the contrast between center and exterior even more, so I decided to leave the potatoes in really large chunks. A full quarter of a potato each. That means each chunk turns into a two-biter, but it makes it easier to crisp them up.

For variety, I tried the three most common supermarket types: russet, Yukon Gold, and red.

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Russets get the crispest crusts and roast up a pale golden brown. Their interiors are fluffy and mild.

Yukon Golds roast a little darker owing to their lower starch content and higher sugar content. This leads to more flavor, but it also means a slightly less crisp crust. Their interiors are nice and creamy, with plenty of flavor.

Red potatoes roast up very dark because of their very low relative starch content, but have difficulty getting crisp. They come out of the oven crunchy, but soon lose that crunch, turning soft and tender.

This is what happens when you press on a russet and a red potato about two minutes after they come out of the oven:

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Moral of the story: Skip the reds. Stick with russets or Yukon Golds (or a mix!).

Playing With pH

In my previous roast-potato recipe, I recommend adding a splash of vinegar to the water for the initial boil. The idea is to control the breakdown of pectin, the cellular glue that holds vegetables together. Think of it as the mortar between bricks.

Pectin begins to break down at around 183°F (84°C), but its breakdown is also greatly affected by the relative pH of the cooking medium. The lower the pH (i.e., the more acidic), the less it breaks down. Conversely, the higher the pH (the more alkaline), the faster it breaks down.

To demonstrate this, I cooked four potatoes in water at various pH levels, ranging from slightly acidic to neutral to very alkaline. You can clearly see that the potatoes boiled in more alkaline water have started to break down more than those boiled in acidic water.

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Which way is better? Well, with the smallish potato chunks in my original roast-potato recipe, adding a splash of vinegar can help prevent the potatoes from accidentally falling apart completely while you are tenderizing them. Similarly, I add a splash of vinegar to my French fries to get them to cook fully without collapsing.

But with a different form factor comes a different set of rules. Is vinegar still the best pH modifier for the job with the huge, chunky potatoes I'm using here?

I roasted those boiled potatoes to gauge the difference.

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As it turned out, the potatoes boiled in alkaline water were actually superior to those boiled in vinegary water. Because the chunks are so large, falling apart is not as big of a problem as it is with smaller potatoes. Meanwhile, the alkaline water helps the exteriors of the potatoes break down more, creating much more of the starchy slurry that leads to an extra-crisp exterior. About a half teaspoon of baking soda for two quarts of water was the right amount.

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That's the level of starchy paste you're looking for on the outside of these potatoes after roughing them up.

Cold Starts Leave Me Cold

Another element worth considering is the way in which the potatoes are boiled. In most potato recipes, I recommend starting potatoes in cold water and bringing them up to a boil. This helps ensure that the exteriors don't turn to mush before the insides have a chance to cook through. It's especially true for larger chunks of potato, because heat can take a good deal of time to travel through to the core.

But here we've got a whole different ball game. We actually want the exteriors to break down more than the centers. That means starting the potatoes in already-boiling water. I made sure to salt the water well (about an ounce of kosher salt for two quarts of water) to season the potatoes as they cooked.

Roasting Right

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Now for the actual roasting bit, which happens to be the easiest part to do but also the hardest part to prescribe, because potatoes vary so much. For instance, take a look above at two Yukon Gold potatoes that I boiled and roasted in a completely identical manner. The only difference was the store where I bought them. In the time it took the one on the left to brown completely, the one on the right was still pale. This has to do with the starch and sugar content in potatoes, which vary not only seasonally but also depending on how long the potatoes were stored, and in what manner.

Don't worry—you can make great roast potatoes regardless, but this does mean that you're going to have to rely on your eyes and nose, using a timer only as a very rough guideline.

I found that roasting the potatoes nice and hot, at 450°F (230°C), was ideal, though with convection turned on, they came out even better. (When using convection, I dropped the temperature down to 400°F/200°C, to prevent the edges from singeing.)

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At the start, the potatoes are a little delicate, and trying to shake them or move them too early can result in the bottoms sticking to the roasting pan. But roasting them without any moving at all leads to uneven cooking. I found that if I left them alone for the first 20 minutes or so, I could then use a thin metal spatula (or my fingertips) to pry them up off the pan and give them a flip. From there, they take another 30 minutes or so, with the occasional flip and shake in the middle. I like to let them get nice and dark to maximize that contrast between crisp exterior and creamy center.

Flavoring Flubs

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The final step in the process is adding some aromatics to make them a little more interesting. Simply tossing the boiled potatoes with chopped herbs and garlic works okay, but it's not ideal. The high heat and long roasting time tend to burn the garlic, giving the potatoes a slightly acrid flavor. But tossing them in chopped garlic and herbs at the end gives them only a superficial flavor. So what's the solution?

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I decided to heat up the solid aromatics (minced garlic and rosemary are my favorites) in some olive oil, cooking them just until the garlic started to turn golden, then strain it, separating the infused oil from the solids. That way, you can use the flavored oil to toss with the potatoes, building in plenty of flavor, and add back the garlic and rosemary (along with some minced fresh parsley) at the end. Best of both worlds.

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You end up with roast potatoes that have an incredibly crisp crust, with plenty of textural variety and lots of microscopic nooks and crannies for flavorful bits of garlic and herbs to plant themselves.

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Did I mention that these are the greatest roast potatoes you'll ever make? I meant it. Take a closer look at their surface texture.

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Micro-blistering!

And how about these creamy centers?

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Oh! So moist! So flavorful!

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Still on the fence about making them? Come on over and join me on this side, where the deliciousness runs deep and there's plenty to go around for everyone.