I've got an original WW1 British Army cookbook amongst my manual collection, but will check the website to see how the earlier one differs
Some of the stuff in the WW1 book sounds brilliant - may have to dig it out now to post examples
As an aside, I was at a Symposium at the Royal Armouries in Leeds a while back, and one of the snipers giving a talk said that "British Army cook" is the 3rd most difficult military qualification - after SAS at 1 and Sniper at 2....
He had this theory, as after several years on active duty he'd yet to meet any b*****d from the Catering Corps that could have passed the course