This is essentially a giant butter cookie, flavored with salt for an amazing salty-sweet experience. With so few ingredients, you must use the best quality products you can; a premium French butter would be ideal. The original recipe calls for gray salt (a moist, large-crystal French salt), but any kosher or coarse salt will do. (Try to avoid iodized salt; the simplicity will just pull up the iodine flavor.) Adapted from a post by Caroline Russock at Serious Eats (which she adapted from _Around My French Table_ by Dorie Greenspan). http://bit.ly/b9Iz1M