Preheat oven to 425 degrees.

Cut sweet potatoes into fries, trying to be as even as possible in your cuts so they all bake at the same rate. I found a cut a bit thicker than a French fry cut works best, just a hair more than 1/4 inch. Thinner cuts tend to shrivel a bit too much.

Place the fries in paper bag and gently shake with two tablespoons of cornstarch. (The amount you need might vary just a bit with the thickness and cut of your fries – they should be just lightly dusted with the cornstarch.) If you do happen to detect a slight cornstarch flavor on the fries, cut back a bit next time.

Place on two baking sheets (don’t overcrowd or they won’t be crisp.) Drizzle with oil and toss until each fry has a very light coating. Use a light hand with the oil. You’re baking, not frying.

Bake for about 10 to 15 minutes, depending on the thickness of the fry and your oven. Watch closely. Turn fries over, with a gentle hand (a thin spatula really helps.) If possible, rotate the outside fries to the inside and visa versa. Rotate sheet pans from top to bottom and front to back. Bake for another five to 15 minutes or so. Watch carefully; ovens vary in temperature and circulation.

A few brown spots are to be expected; too many will make the fries bitter.

Remove from oven and sprinkle with salt or other seasonings while still warm – this is a great place to pull out a sea salt.

If not using all immediately, a wire rack will help preserve the crispness.