Preheat oven to 325F. Line baking sheet with parchment paper and lightly spray with cooking spray. Set aside.
Using a mandolin, slice yams into paper-thin slices.
Line baking sheet with yam slices, overlapping slightly on the edges. Spray well with cooking spray, then transfer to oven.
Bake for 25-30 minutes, until edges curl up and are crisp. Dust with cinnamon for an extra boost in sweetness. Allow to rest for 5 minutes to crisp up even more before serving.