Cook

In chess composition, a cook exists when there is a valid solution beginning with a first move different from the one intended by the composer. It is not merely a promising alternative: the extra line must actually satisfy the stipulation, meaning the task stated by the problem.

The first-move distinction matters. If two valid continuations appear after the same correct first move, the defect is called a dual, not a cook. If the composer explicitly stipulates multiple solutions, those solutions are intended content and are not cooks either.

In a mating problem, a cook competes with the intended key, the correct first move; in a proof game, a legal sequence constructed from the initial position to the diagram, an unintended route can likewise matter when the stipulation requires uniqueness. Finding a cook usually means the composition is technically unsound unless its stated conditions permit that multiplicity.