Preheat oven to 325 degrees. Whisk sugar and flour in a bowl. Add whites, then butter; whisk until smooth.Advertisement
Line a baking sheet with a nonstick baking mat. Coat mat with cooking spray. Spread 1 teaspoon of batter onto prepared sheet in a 3 1/2-inch-wide circle. Repeat, spacing circles 2 inches apart. Bake until tuiles begin to turn golden brown, about 12 minutes. Remove from oven, and place sheet on a wire rack. Working quickly, roll 1 cookie at a time: Flip it over, roll it tightly around a chopstick, then slide it off and place on a cool, flat surface. Repeat. If the cookies become brittle, return them to the oven for about 30 seconds.
These cookies must be rolled straight out of the oven; otherwise they will become brittle too quickly and break as you are trying to roll them.