Dark chocolate, also called "black chocolate", is produced by adding fat and sugar to cocoa. It is chocolate with no milk or much less than milk chocolate. The U.S. has no official definition for dark chocolate but European rules specify a minimum of 35% cocoa solids. Dark chocolate can be eaten as is, or used in cooking, for which thicker, more expensive baking bars with higher cocoa percentages ranging from 70% to 99% are sold. Dark is synonymous with semisweet, and extra dark with bittersweet, although the ratio of cocoa butter to solids may vary.