Until recently, I was suspicious of sweet potato fries as a concept: they seemed a misguided attempt to make chips healthy, with recipes that sang the praises of “non-starchy carbs” inevitably turning out sadly soggy results.
Frankly, five-a-day points aren’t one of the things I look for in a fish supper – that’s what mushy peas were invented for, surely. Then, while travelling in the Caribbean, I had a revelation: crisp sweet potato fries that made a virtue of the tuber’s natural sugars to give a deliciously caramelised result. They weren’t trying to be potato chips – which is fortunate, because their strong flavour and dense, creamy texture is never going to fool anyone – but this time, they were just as delicious.
Having failed to charm the secret out of staff, I turned to the internet, only to find a litany of threads with plaintive titles such as “Why didn’t my sweet potato fries get crispy?” and disgruntled comments underneath “addictive” recipes from usually reputable sources along the lines of, “I’ve cooked this four times and have never managed to get them crispy.” Clearly, this was going to be harder than it looked. So what is the secret to perfect sweet potato fries?
The potatoes
Some recipes specify there’s no need to peel, but, though generally a fan of the lazy approach, here I think a little work pays off: the skin makes the fries taste like baked potato wedges rather than chips.
Cook’s Illustrated magazine cautions that “the typical sweet potato fry is cut thin, which means too little creamy sweet potato interior”, and I’m inclined to agree: much as I love french fries, the sweet potato has a tendency to dry out if prepared like this. Instead, make a virtue of its dense texture by cutting them into wedges, which will allow the interior to remain fudgy while the exterior crisps up.
Sweet potatoes do have a relatively low starch content in comparison with the ordinary kind, but, just as when cooking rice, it’s important to get rid of as much of that as possible before cooking, because it will turn into sugar, which burns at high temperatures – some, such as Rebecca Lindamood of the Foodie With Family blog, reckon that excess starch stops the fries getting crisp – though rinsing, as with rice, should do the trick; there’s no need to soak them for hours first.
Cook’s Illustrated and The Joy of Cooking both pre-cook their wedges first, which makes sense from my experience of ordinary chips – and means that thicker-cut wedges will cook through before the sugars on the outside burn. The former adds some bicarbonate of soda to the water, which makes the outside of their chips a bit “tacky”… which will prove useful in the next step. Frankly, their recipe is just about perfect, so I’ve stolen their method. Thanks, guys.
The coating
The Joy of Cooking fries its par-boiled potatoes without further ado, but everyone else coats them in some way before cooking.
Alice Hart cautions in The New Vegetarian that sweet potatoes should not be seasoned with salt until the last minute: “It will only draw moisture out and make the sweet potato soggy.” Instead, she coats hers in cornflour, cornmeal hot paprika and dried garlic. Jamieoliver.com has no fear in adding salt, along with sweet smoked paprika and black pepper, while Cook’s Illustrated sticks with a simple paste of cornflour and water, which does indeed cling to the tacky exteriors of their par-boiled fries very effectively.
Seasoning alone doesn’t seem to cut the mustard: the jamieoliver.com wedges are tasty, but soggy rather than crunchy. Having removed excess starch from the potatoes themselves, it’s time to add some back on to the surface to crisp up in the heat. Hart’s mix pleases testers the most: the cornflour provides an even coating, while the cornmeal adds a gritty crunch. Jamieoliver.com’s smoked paprika is optional, but recommended. As my recipe involves parboiling the potatoes first, it seems wise to salt the water rather than the coating, just in case any moisture might be drawn out.
The cooking
Look, I wanted to give you an oven-baked recipe, I really did – I made three of them and they were fine. But the truth is that, just as you can’t make truly great chips without frying (no, you can’t. Don’t fib), it’s not fair to deny the sweet potato the chance to fulfil its potential.
If you really must bake them, then use Hart’s recipe (25-30 minutes at 220C (200C fan)/425F/gas 8), it’s good, but not as good as the magnificent fries from Cook’s Illustrated, which are snaffled before I’ve even finished frying the second batch. I’m sorry, but hot fat is the price you’re going to have to pay for perfection. Deal with it.
The seasoning
They shouldn’t need much more than a sprinkling of salt, but if you’re feeling really all-American this Thanksgiving, you might enjoy The Joy of Cooking’s suggestion to dust the fries with a mixture of brown sugar and nutmeg as well. Marshmallows sadly aren’t mentioned, but they’d probably work, too.
Perfect sweet potato fries
Prep 15 min
Cook 15 min
Serves 4-6
2 large sweet potatoes
2 tbsp salt
1 tbsp bicarbonate of soda
100g cornflour
1 tbsp smoked hot paprika (optional)
100g cornmeal or polenta (optional)
750ml neutral oil, for deep-frying
Peel the potatoes, then cut them into wedges about 2cm thick. Rinse very well in cold water.
Put two litres of water in a large pan, add the salt and bring to a boil. Add the bicarb, then cook the wedges for about five minutes, until soft on the outside but still hard in the middle. Drain well.
Mix the cornflour with 120ml cold water and the paprika, if using, to make a thin paste, then add the wedges and stir to coat.
Spread the cornmeal, if using, on a plate, then briefly roll the chips in it to coat lightly all over.
Put the oil in a large, nonstick frying pan about 30cm in diameter and bring to 180C/325F. Meanwhile, line the grill pan with foil and put in a low oven.
Fry the chips in small batches until deep golden and crisp (the paprika, if using, will make it harder to tell, so look at the potato underneath), turning once, then scoop out with a slotted spoon and put on the grill rack to keep warm. Repeat with the remaining sweet potatoes, making sure the oil comes back to temperature before cooking the next batch.
Season to taste and eat immediately.
