How to Bake Crispy Sweet Potato Fries

by Elizabeth Skipper | September 17th, 2014 | Ask the Chef

sweet-potatoes-996_640I love baked sweet potato fries. However, no matter what I’ve tried (high heat, tossing in olive oil/cornstarch/flour, greasing the pan), I don’t get crispy fries. Is there a way to bake sweet potatoes and get crispy fries?

Good question! I usually simply bake sweet potatoes, so this required some research. I wasn’t able to ascertain whether the starch in sweet potatoes and white potatoes is the same, although they’re both high in starch in the form of carbohydrates. I was wondering if sweet potatoes have more natural sugars, which might explain your problem, as sugars caramelize rather than crisp. Couldn’t find that answer, though, so how else to approach this?

Of course you already know you can get crispy fries by deep frying them. Believe it or not, deep frying is actually a dry heat method of cooking. How can we apply some of the same principles to baking? To deep fry properly, the surface of the food should be dry; sometimes it’s coated with a starch or batter to seal in the moisture. Oil or fat used for deep frying should not break down under high temperatures of between 325° and 400°F. And the pan should never be crowded, or the temperature of the oil will be lowered, with the result that the food won’t be crispy. Let’s apply those principles to refining the techniques you’ve already tried to see if we can reach your goal.

Here’s what I suggest you try. Preheat the oven to 400°F for a full 15 minutes or more. Air doesn’t conduct heat as well as oil, so you want a pretty hot oven (although not so hot the outside of the fries overcooks before the interior does.) If you have a convection oven, use that feature. The circulating air will aid in keeping the surface of the fries crisp.

Toss the sweet potatoes in enough of an oil like peanut oil, which can take the heat, to coat them thoroughly, and season them to taste. Add salt, which will tend to draw moisture to the surface of the potatoes, just before they go into the oven.

Use a heavy sheet pan, and lightly coat it with a little more oil. Then preheat the pan, too, so the potatoes begin to sear when they come into contact with it. Work quickly, and don’t crowd the pan – be sure there’s room between each fry, so there’s no steaming.

When I bake white potatoes this way, I check on them after about 15-20 minutes, to see if they’re browning. Usually they are, and will come away from the pan easily with careful use of a flexible metal spatula. (Speaking of which, my favorite such item came to me second- or third-hand. Nowadays, they all seem to be thick and stiff, useless for delicate work. Find a good one at a thrift shop or antiques store, or ask your mom or granny to will you hers. Or dad or grandpa – shouldn’t show prejudice, right?)

Turn the fries to brown the other sides and continue to bake until done, probably about another 15 or 20 minutes – maybe less if using a convection oven. Test with a skewer to ensure they’re tender throughout. If you’re not happy with the browning, and they’re cooked, you can run them under the broiler briefly; but keep an eye on them! It would be a shame to burn them now. Serve before they have a chance to get soggy.

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