There is an interesting history as to why peanut butter cookies have criss cross fork marks! This way of making peanut butter cookies first appeared in the Schenectady Gazette on July 1, 1932 and then grew in popularity when Pillsbury published a cookbook in 1933 that referenced this technique. Beyond the interesting history of this technique, putting fork marks on the top of your peanut butter cookies does help them to cook evenly, given the dense nature of the dough.