Step 1
Set the oven to 350°F and spray two baking sheets with cooking spray for at least three seconds each.
Step 2
Peel the sweet potatoes and cut them in half crosswise. (This makes them a little easier to handle.) Cut each half into slices no thicker than 1/4 inch. Stack two or three slices at a time and cut strips no wider than 1/4 inch.
Step 3
In a medium-size bowl, beat the egg whites with a fork or a whisk for about a minute until they are frothy.
Step 4
Place the potato strips into the bowl and gently toss them with your fingers to coat the egg whites.
Step 5
Using your fingers, pull the potato strips out of the egg whites--a few at a time--and lay them on the baking sheets in a single layer. The potatoes should not touch each other. (Wash your hands immediately after this step.)
Step 6
Bake the potatoes for 30-35 minutes, checking them after 15 minutes to make sure they're browning on the bottom but are not turning completely brown.
Step 7
Remove the baking sheets from the oven and sprinkle the potato chips with salt and pepper (if desired). Use a spatula to remove the chips from the baking sheets. (You may need to use a bit of force, but most of the chips should remain intact.)
