Bob writes: Loved your recent article in Fine Cooking for getting french fries just right. Could you enlighten me on how to get the same great result for sweet potato fries?
Tony’s take: Ok, I know this is going to look like I planted a fan letter and while I’m totally not above that, I actually received this note from Bob and because I’m shameless, I’ll run it. The question is a good one, and one for which I’ve given a lot of thought (that picture is of some of the 1000 lb. of sweet potatoes that we cook each day at b.good). Perhaps even more than regular potatoes, making sweet potato fries requires finesse. Sweet potatoes’ high sugar content can quickly push them across to the wrong side of the browned/burnt balance. The solution for this sugary situation (and the one big difference between these and regular fries) is that you’re going to want to fry sweet potatoes at a relatively low temperature. As with fries, I like to double-fry sweet potatoes (the two stages of cooking ensure that the interior gets soft and creamy and the exterior nice and crisp), but I like to cook them at around 310F on the first cook and 350F on the second cook (as opposed to the 330F and 360F that I advise for fries). The other big difference between the way I treat these and regular fries is that I like to cut sweet potatoes slightly larger (about 3/8 inch or the size of your pinky finger) so they have a little substance; this makes up for the fact that they can never get quite as crisp as regular potatoes. Beyond these two steps, most everything else with sweet potato fries is relatively simple and similar to regular fries. Most any kind of sweet potato at the market should do just fine for this technique (larger ones are easier to cut uniformly), do make sure to cut them evenly so they cook uniformly (sweet potatoes are very dense, so you’re best off using a knife as opposed to a cutter), and then hit them with salt and a dusting of spices (chipotle powder, chile powder, garlic powder, and brown sugar) if you like before serving.
Serves 4 as a side: Prep time: 10 minutes. Cook time: 20 minutes
What you need: Ingredients: Sweet potatoes (about 1 1/2 lb, about 2 large), canola oil or peanut oil (you’ll need about 2 quarts), salt. Make a light spice rub (see above) if you like.
Equipment: Cutting board, chef’s knife, large pot (it needs to be large enough to hold at least 8 quarts), deep-fry thermometer (or candy thermometer), large slotted spoon (a “spider” if you have), tongs, large baking sheet, paper towels.
How to do it: Heat the oil and cut the potatoes: Add some oil (canola or peanut) to a pot so it’s between 2 and 3 inches deep and heat it over medium heat until its temperature hovers around 310F, 4 to 5 minutes. Meanwhile, using a chef’s knife, cut the sweet potatoes uniformly into fries somewhere between 1/4 and 1/2 inch thick (trim the ends of the sweet potatoes, next cut the potatoes into disks of this thickness, and then cut the disks into sticks so you get fries about 3/8 thick).
Fry the sweet potatoes once: Drop about half of the sweet potatoes into the oil and cook, shifting them around with tongs, until the sweet potatoes become soft and tender (they may brown lightly), about 3 minutes. Transfer to a large baking sheet lined with paper towel using the slotted spoon (try to shake off excess oil before making the transfer) and sprinkle generously with salt. Fry the remaining sweet potatoes in the same manner. At this point, the once-fried sweet potatoes can hold at room temperature for up to 4 hours if you want to prep them ahead.
Raise the oil temperature and fry the sweet potatoes a 2nd time: Raise the heat slightly so the oil hits 350F. Add half of the sweet potato fries and cook, stirring occasionally, until they brown but don’t burn (it’s ok if the tips burn just a bit), about 2 minutes. Transfer to another baking sheet lined with fresh paper towels, sprinkle with salt, and lift the edges of the paper towels up so they make a pouch out of the fries and shake to dry off any excess oil and to distribute the salt uniformly. Serve immediately and fry the remaining sweet potatoes in the same manner.