American author Richard Fortman noted in "America's Best Checkers" (ABC) that the word "Cook" is a jargon expression of uncertain origin, peculiar to the game of draughts.
It is believed that it was used in years gone bye to describe a move which initiated a new attack or defence that a player would have "cooked up" in preparation for playing an opponent, or a new combination to "spice up" a familiar position.
It has been interpreted by differing authors to mean similar things, and I believe that Asa Long's definition - "My idea of a cook is for a player to spring a new line, previously prepared, on an opponent" is accepted as what we mean when we use the word. This definition is similar to Derek Oldbury's description as "an innovation prepared in advance". We can therefore see that a "Cook" has two components, i.e. a new line of play, and one that has been previously prepared.
So what makes a "Cook" effective? For a "Cook" to be potent it also requires a third ingredient - good timing. Tom Wiswell noted in his book "Learn Checkers Fast" that a "cook" is "… usually kept a secret until it can be used to good effect in an important match or tournament." The element of surprise therefore increases the potency of the "cook".
Many "master" players have developed personal techniques for putting their "cooks" on against their opponents. Derek Oldbury favoured slowing down his play (taking more time over his moves) prior to reaching the position where he would spring his "cook", creating the illusion that he was unfamiliar with the play at hand. When he eventually played his new innovation, his opponent wasn't sure if it was a "cook" or a mistake!
Willie Ryan mentioned a fourth ingredient when he related that a good "cook" should give your opponent choices to go wrong. He noted that ideally such an innovation should be "an exceedingly hard move to meet on a first try". The more choices it offers the greater the chance of your opponent making a weak replay. Walter Hellman also advocated that the earlier a "cook" could be played in a game, the greater the chances of success.
Wm. Ryan was also known for adding a bit of colouring to his cooks (of the descriptive kind) giving them memorable names such as his self styled "Cook of the Century" and his "Atomic Cook".
Drawing these themes together, we see that a "cook" is a new move, previously prepared in advance, played at the right time and opportunity for maximum effect, giving as much choice of replay as possible.
Take the following example … Wm. Ryan was playing Marion Tinsley in the final round of the 1946 US National Tournament. Ryan was a game down after the nine games played, and desperately needed a win in their final game to draw the round.
Playing with the White side of 11-15 23-18 12-16 18x11 8x15 24-20 9-14 20x11 7x16 Ryan introduced his self styled "Atomic Cook" with 22-17! (22-18 was the standard play at that time) 4-8 26-23 8-11 (15-19 now known to be best) 25-22 16-20 17-13 5-9 28-24 3-8 22-17 15-18 29-25 8-12 30-26 11-15 32-28 and Tinsley resigned, allowing Ryan to tie the round, and enabled him to go on to win the tournament.
For a more recent example, players might remember the last game of the Irish Open Championships 1998 between Hugh Devlin and Tom Watson, where a "cook" prepared seven years previously decided the championship winner.
Some authors have been known to attribute a move that is new to them as a "cook" in error. Later discoveries might show the move in question to have been relatively well known in a former era. For example, in a 1926 Masters tournament in the USA, Saul Weslow played what looked like a new move in his match against Sam Gonotsky, with Gonotsky describing it as a "cook" in the annotations "which came as a complete surprise!". A later discovery revealed that it was earlier shown by Joshua Sturges in his "Guide to the Game of Draughts" back in 1800! These errors are all too common in modern draughts literature.
There are some players who in the course of a game make a speculative move (not previously prepared) which may turn out to be strong, maybe even scoring a win, and they proudly announce that the move played was a "cook"! Further analysis might show that the move played was in fact very weak if met by a stronger combination. It's even been known that such a "cook" was proven to be a total loss! Students must therefore beware, and take into consideration who the chef was!
"Don't touch anything that's only half cooked!"