Okay, this time I'm cheating. It's not actually a book about food; it's a short-story. But when the topic of food got brought up, the first thing that popped into my head was Patricia C Wrede's Quick After-Battle Triple Chocolate Cake from the short story "Utensil Strength," which also features my favourite weapon of all time: the Frying Pan of Doom.
There is actually a recipe for Quick After-Battle Triple Chocolate Cake at the end of the story. I've made it. It's actually pretty good, although it doesn't rise much and can have an almost brownielike consistency. I recommend turning it into a two-layer with chocolate frosting.
(Image copied from Aelia Reads: http://aeliareads.wordpress.com/2010/05/05/chocolate-cake/)
"Utensile Strength" is the last story (as far as I know) in the Enchanted Forest series, which begins with the marvellous Dealing with Dragons, one of my childhood favourites.
Book of Enchantments has quite a few good stories, including an interesting retelling of "Twa Sisters" and a memorable version of Sleeping Beauty.