A snickerdoodle is a type of cookie that is popular in the United States, particularly in New England. It is made with flour, fat, sugar, and salt, and rolled in cinnamon sugar. Eggs may also sometimes be used as an ingredient, with cream of tartar and baking soda added to leaven the dough. Snickerdoodles are often referred to as "sugar cookies," but traditional sugar cookies are often rolled in white sugar, whereas snickerdoodles are rolled in a mixture of white sugar and cinnamon. Cream of tartar is added for its signature texture as another main difference.

The key features of a perfect snickerdoodle cookie include being soft and chewy, having a signature tang from the cream of tartar, and being rolled twice in cinnamon-sugar to ensure that it is completely coated. The process of making it is similar to many other cookies, and it can be made with simple ingredients such as butter, sugar, flour, cinnamon, and cream of tartar.

The origin of the snickerdoodle cookie is not entirely clear, but some food historians argue that it is German in origin, while others trace its origin to New Englands tradition of whimsical cookie names. The name "snickerdoodle" may be a corruption of the German word Schneckennudel, a Palatine variety of schnecken, or it may be a nonsense word with no particular meaning.

In summary, a snickerdoodle cookie is a type of cookie made with flour, fat, sugar, and salt, and rolled in cinnamon sugar. It is soft and chewy, has a signature tang from the cream of tartar, and is a popular cookie in the United States.