To make the perfect restaurant-style sweet potato fries at home there are a few things you need to know:
- Size matters – cut the potatoes uniformly. This will ensure they all cook at the exactly the same time, thus having the same texture.
- Soak in ice water – there are 3 things this does: removes the starch (i.e. sugars) that’s on the surface of the potato prevents them from browning prematurely before the insides are fully cooked, cools the slices so they will cook a bit slower initially, creating a perfectly fluffy inside, and allows less oil to be absorbed during frying.
- Lightly dust with cornstarch – tossing the slices with a bit of starch and letting the slices sit for 20 minutes, absorbs the remaining surface moisture which in turn gets fried into a super crispy crust. Cornstarch is the best however if you are allergic, arrowroot or potato starch can be used instead.
- Choose the right oil – an oil with a high smoke point is necessary for deep frying, as well as one that has a neutral flavor. Peanut is the best followed by corn oil, however if you have an aversion to either of these use whatever (higher smoke point) oil you are comfortable with.
- Fry twice – the key to fries with a crispy outside and tender insides are a two-stage (and two-temperature!) frying method.
Sweet potatoes are best cut plank style – 1/4″ thick by 1/2″ wide. This gives more surface area to cook them, making them crispy instead of mushy-which tends to happen with this type of potato.
Soak the cut slices for 30 minutes in very cold water (with ice or in fridge) to remove as much starch (natural sugars) as possible from their surface, this will ensure they don’t brown during their first frying. Drain and dry them completely before frying. Then toss with a bit of cornstarch, and let sit in a wire rack for 20 minutes to allow the cornstarch to create a light film over the fries.
The first fry at the lower temperature will soften the fry, it should be tender enough to cut with the side of a spoon. Once they reach this point, scoop out and lay on paper towels. Make sure to cook in batches – frying too many at one time will lower the temperature of the oil too fast and it will take longer to cook them properly (and they will absorb more oil). Make sure the fries rest for at least 10 minutes before staring the second fry – this allows the starches on the surface to create a thin film (which will turn into the final crispy crust).
Increase oil temperature and fry in batches. The second fry at the higher temperature, is what gives the fries that deep golden color and crispy outside.
Once done, immediately drain on a wire rack for a few seconds (shaking to remove any excess oil) then put into a bowl and toss with salt. You don’t want the fries to drain on a paper towel at this point, since the crispy edges of the fries against the damp paper towel will start to soften the crispy outsides.
(Deep-Fried) Sweet Potato Fries
- 2 1/2 lbs large sweet potatoes peeled
- 2 Tbsp cornstarch
- Deep-frying oil*
- Cut potatoes plank style - 1/4" thick by 1/2" wide. Place in a large bowl of cold ice water and chill in fridge for 30 minutes, changing water 3 times. Drain, pat completely dry.
- Place cornstarch in a large bowl and gently toss with potatoes to coat. Shake off excess and place on a wire rack (over a baking sheet) and let sit for 20 minutes to allow the cornstarch to form a white coating over the potatoes.
- Choose a heavy bottom sauce pan and fill at least 4" deep with oil (making sure you have 3-4" headroom at top to allow for the oil to bubble up). Bring oil up to 330°F using a deep-fry thermometer, then carefully drop a third of the potatoes into the oil. The ideal temperature of the oil is 325°F for cooking, however by increasing the heat initially at the start it will compensate for the drop in temperature once you add the potatoes.
- Gently stir the potatoes around and remove after 3-5 minutes when they can easily be cut with the side of fork, and their surface just starts to blister (but not brown). Use a mesh strainer and remove the potatoes from the oil, and place on a paper towel lined pan wire rack (with a baking sheet underneath). Fry the remaining potatoes the same way. Be sure not cook too many at once - this will dramatically lower the temperature of the oil, you want to maintain the temperature at 325°F during this initial fry. Let the slices sit for at least 10 minutes before the second fry (this will firm up the cornstarch coating).
- Increase oil temperature to 375°F then fry in batches for 1-2 minutes or until potatoes turn golden brown and are crisp. The ideal temperature of the oil for the second frying stage is 350°F, however by increasing the heat initially at the start it will compensate for the drop in temperature once you add the potatoes.
- Immediately strain out and place on wire rack (remove paper towel), shaking to remove any excess oil. Place fries into a bowl and generously sprinkle with salt. Repeat with remaining potatoes.