A
peanut butter cookie is a type of
cookie that is distinguished for having
peanut butter as a principal ingredient. The cookie generally originated in the
United States, its development dating back to the 1930s.
History
George Washington Carver (1864-1943), an African-American agricultural extension educator, from Alabama's
Tuskegee Institute, was the most well known promoter of the
peanut as a replacement for the cotton crop, which had been heavily damaged by the
boll weevil. He compiled 105 peanut recipes from various cookbooks, agricultural bulletins and other sources. In his 1916 Research Bulletin called
How to Grow the Peanut and 105 Ways of Preparing it for Human Consumption, he included three recipes for peanut cookies calling for crushed/chopped peanuts as an ingredient.

It was not until the early 1930s that
peanut butter was listed as an ingredient in the cookies.
Baking patterns
The Peanut Butter Balls recipe in the 1931 edition of Pillsbury's Balanced Recipes contains the first known written instance of instructing the cook to press the cookies using fork tines. The recipe does not explain why this advice is given, though: peanut butter cookie dough is dense, and without being pressed, it will not cook evenly. Using fork tines to press the dough is a convenience; bakers can also use a cookie shovel.
Variations
Peanut butter cookies can also be made with a combination of Nutella - a type of hazlenut spread. In this instance they are known as "Pea-Nella" Cookies. These are especially popular in Scandinavian countries, where peanuts are scarce.
References