Mushy sweet potato fries make us sad. Far too often they’re flimsy and limp, and passed off as a more sanctimonious way to eat french fries. But sweet potato fries deserve better. They have all the potential to be as shatteringly crispy as any regular fry, with all the extra flavor and sweetness we’ve come to love in sweet potatoes.
You can have all this without deep frying, double soaking, twice baking, or anything so involved. For the crispiest oven-baked sweet potato fries, you need to walk over to the pantry and take out the cornstarch because that ingredient is the secret.
“Oh How It Wishes It Were a French Fry”
One of my favorite dinnertime memories involves sweet potato fries and my daughter when she was just 2 years old. I had attempted oven-baked sweet potatoes fries as a side for dinner. After my daughter sat down to eat, she picked a limp sweet potato fry from her plate and sighed, “Oh how this wishes it were a french fry.” Since that night, I’ve tried and tested at least a dozen different methods for baking sweet potato fries that are actually crispy. Nothing like a wistful 2-year-old to kickstart a culinary journey.
Fast forward a bit and that journey has brought me here. Today I can confidently say that the secret to crispy, oven-baked sweet potato fries is a combination of extra starch and oil. They work together to create a thin coating on the fries which, when baked, becomes delightfully crispy while the sweet potatoes soften. With the simplest of changes we end up with a crispy sweet potato fry with a soft interior that is still sturdy enough for dipping.
Why Does Cornstarch Make for Crispy Baked Fries?
Take a gander at the ingredient lists of the many frozen sweet potato (and for that matter, plain ol’ potato) fries available in the grocery store and you’ll likely see a common ingredient: starch. Some manufacturers use rice, tapioca, or even potato starch to coat their fries to crisp them. No matter the starch, the role is the same. Pure starches have an uncanny ability to absorb moisture before being cooking by the oil and setting into a rigid (i.e., crispy) crust.
You’ve probably read about soaking your fries overnight or frying them twice for a really crisp exterior. Both of those steps put a lot of time between you and delicious sweet potato fries. Instead, we go straight to the point and rely on the pure starch of cornstarch to create a crisp coating.
Use Potato Starch If You Can
Potato starch makes these sweet potato fries next-level delicious, so feel free to use that if you’ve got it. Most of us don’t keep several starches on hand, so I chose the most common starch for this recipe.
The Essentials for Making Crispy Sweet Potato Fries
Making baked sweet potato fries isn’t quite as simple as cutting up sweet potatoes and then baking them, but it’s pretty close! Technically you want to roast (not bake) these fries, so set your oven to 400°F and give it time to thoroughly heat.
You need a large sweet potato in the one-pound range. Peel the sweet potato and cut it into quarter-inch-thick wedges. Then the guaranteed secret for success is to toss those fries with cornstarch and salt, followed by oil. Place the sweet potatoes in an even layer on an ungreased baking sheet. Bake the fries for 20 to 25 minutes, flipping only once.
A Few Tips for the Best Baked Sweet Potato Fries
- Cut the potatoes as evenly as possible: The more uniform the fries, the more evenly they will bake. Aim for 1/4-inch thickness. Large fries will take too long to bake, while thinner fries will bake up greasy and limp.
- Coat the sweet potatoes well: You can toss the potatoes with the cornstarch, followed by the oil, in a large mixing bowl, but I prefer a gallon-sized zip-top bag, a la shake-and-bake. It gives a more even coating and, most importantly, I can task my kids with this step.
- Roast them, don’t bake them: A long, low bake (say 375°F or below) will result in tender sweet potatoes, but never crisp. Instead crank the oven to 400°F for a hot, fast roast. It’s a critical step for a crisp coating and tender interior.
- Flip them once, never more: You might think that flipping or turning the sweet potato fries while they bake would make for more evenly cooked fries, but the coating needs time to set before you flip the fries.
Seasoning Your Crispy Oven-Baked Sweet Potato Fries
Once you master this basic oven-baked sweet potato fry, you can play with the salt and add spices as long as you always coat the potatoes in the cornstarch and seasoning before coating them in the oil. We occasionally do these sweet potato fries with a teaspoon of sugar and a 1/4 teaspoon of cinnamon added to the cornstarch before baking as a sweet after-school snack. You can add garlic, onion, or ginger powder. Smoked paprika added to the cornstarch adds a ton of flavor and makes for darker sweet potato fries. Pairing these crispy sweet potato fries with your favorite sauce is also highly recommended.
We know how much everyone loves sweet potato fries, so I retested this recipe and made just one notable change: Roasting the fries on two baking sheets instead of one gave the fries plenty of room to really crisp up instead of steam. When coating the sweet potatoes with the starch, make sure that all of the starch is absorbed before adding the oil to ensure an even coating that creates the crispy exterior we all know and love in a good fry. My daughter loves this recipe so much it’s been requested multiple times!
—Christine, July 2018
How To Make Baked Sweet Potato Fries
Yield: Serves 4
- 1 pound sweet potatoes
- 2 tablespoons potato starch or cornstarch
- 1/2 teaspoon kosher salt
- 3 tablespoons vegetable oil
Heat the oven to 400°F. Arrange 2 racks to divide the oven into thirds and heat to 400°F. Line 2 rimmed baking sheets with parchment paper if desired.
Peel and cut the sweet potato. Peel the sweet potatoes. Cut in half lengthwise. Turn onto the cut side, then cut lengthwise into 1/4-inch wide planks. Lay the planks flat and cut lengthwise into 1/4-inch-thick sticks or wedges.
Coat the sweet potato in starch. Place the sweet potato in a large zip-top plastic bag or bowl, add the potato starch or cornstarch and salt, and shake or toss to combine until all the starch is absorbed into the sweet potato.
Coat the sweet potato in oil. Add the oil and toss vigorously to coat.
Transfer to 2 baking sheets. Divide the sweet potato among the 2 baking sheets and spread into a single, even layer, leaving space around each fry.
Roast. Roast until some of the fries are just starting to brown around the edges, about 15 minutes. Remove the baking sheets from the oven. Using a flat spatula or turner, flip the sweet potatoes. Place back in the oven, switching the sheets between racks, and continue to roast until the fries are tender on the inside and crispy on the outside, 5 to 15 minutes more. They will crisp up a little more as they cool.
Season and serve. Sprinkle with more salt if desired before serving.
Note: These sweet potato fries are best eaten the day they are made.
Meghan Splawn is the Food Editor for Kitchn's Skills content. She co-hosts a weekly podcast about food and family called Didn't I Just Feed You.