To age egg whites, place 8 to 12 egg whites in a medium bowl. Cover with plastic wrap, and let stand at room temperature for 3 to 6 hours. Alternatively, egg whites may be collected over the course of a week or a month and kept in an airtight container in refrigerator. Let egg whites come to room temperature before using.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/macarons/