Cookie dough and cake batter have much in common: fat, eggs, sugar, and
In both cases, a successful recipe’s ingredients combine together to make a consistent dough or batter. Yet these two kinds of baked goods have very different consistencies.
Cookies are mixed to make dough – a thicker, denser texture. Cakes are mixed as a much thinner batter.
Two classes of ingredients conspire to make dough and batter different from each other
Cakes contain larger amounts of liquids (water and milk, for instance) than cookies. Liquid binds ingredients together and serves to make the batter as thin as possible, which allows bubbles – responsible for a cake's fluffiness – to form more easily.
Despite a descent from cakes and other sweetened breads, cookies use lower amounts of liquids. Fats (butter, eggs, vegetable oils, or lard) are the binding agent in cookies, rather than liquids. Fats are thicker than liquids. The result is thicker dough that is dropped, placed, or spread on a pan in small amounts, rather than poured. As a cookie bakes, the fats in the dough coat the flour particles, seal in starch (to give the cookie shape), and remain in the batter rather than evaporate. The result is a crisper texture.
Leaven (substances like baking powder, baking soda, or yeast) cause dough or batter to expand. Cookie recipes designate smaller amounts of leaven than cake recipes. Less leaven means cookies do not rise as much as cakes do, giving them a more concentrated density.
Home chef and culinary author Michael Ruhlman offers proportions of the ingredients (by weight) for basic preparations.
While you can use all-purpose flour for baking a cake, but cake flour is lighter and adds to a lighter texture.
Cookie recipes, on the other hand, usually call for all-purpose flour.
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