"These keep for several days in an airtight container. You can make the dough in advance and freeze it, too. (Chill it in the refrigerator until firm enough to handle, and then form into a log about 12 to 14 inches long. Wrap well in a double thickness of waxed paper, twisting the ends closed, and freeze. Then, when you want cookies, slice off pieces with a sharp knife, adding about 2 minutes to the total baking time.)..."