Sweet potato fries need their own approach because they soften and brown differently from russet fries. Cut the peeled potatoes into quarter-inch sticks and give them a very light cornstarch dusting before the oil, so the coating stays thin enough to cling without leaving chalky patches. There is no water soak in this recipe; dry sticks and room in the basket matter more than treating them like the white-potato fries above. Shake gently halfway through each batch and watch the narrow tips near the end, because the natural sugars can darken before every broad surface looks deeply browned. They will be a little more tender than a diner basket of deep-fried russets, so serve them promptly and judge success by browned edges around a soft orange center.