How to Make It
Preheat oven to 250ºF. Line 2 large baking sheets with foil.
Using a mandoline or a very sharp chef's knife, slice sweet potatoes very thinly (1/8- to 1⁄16-inch thick). Try to make the slices as uniform as possible to ensure even cooking. Place slices in a large bowl, add oil, and gently toss with your hands to coat potato slices. Season lightly with salt.
In a small bowl, combine sugar and cinnamon. Add about ⅔ of mixture to bowl and gently toss to coat.
Mist sheets with cooking spray. Spread potato slices on sheets, taking care not to let them overlap. Bake for 1 hour. Turn slices over, mist with cooking spray and sprinkle with remaining cinnamon-sugar mixture. Bake 25 to 35 minutes longer, until chips are golden. They will crisp up as they cool.