I first tasted sweet potato fries in a restaurant nine years ago and tried various methods of making them fried or roasted, but could never get them as crispy as desired.
I found a bag of frozen ones I like, which is handy, but think they're spendy -- around three dollars per pound.
I began looking at recipes for the secret or trick for fresh crispy sweet potato fries and at the link, found a method using a coating of corn starch.
I deep fry mine, but the site suggests they can also be baked in the oven. Fresh ones are three to four times cheaper than frozen and worth the effort.
Crispy Sweet Potato Fries
• Cut desired amount of peeled sweet potatoes into thick pieces, about a half inch. Depending on size, allow one or two potatoes for two people.
• Soak cut fries in water a few hours and drain. Rub in one or two tablespoons of oil, then coat with corn starch.
• Put corn starch in a plastic bag and drop several fries in at a time, shaking bag to "lightly" coat fries.
• Lay fries out, not crowding, on a non-stick cookie sheet.
• Either bake in 425 oven for 30 minutes, turning over after 15 minutes, or deep fry at 350-375 degrees for a minute or two, until golden brown.
Serving with favorite dipping sauces.
Estimated cost for two servings: .90 cents.