This is a really fun assignment, really engaging.
As a teacher, I would suggest going with the spirit of the assignment, instead of trying to find a book that mentions a recipe that you find easy.
The point of the assignment is that you share something from a book you enjoy, and because so many books mention food at some point, you are not going to be too limited.
Choosing a book solely for the recipe means that you may very well end up choosing a book you don’t like, and end up not really reading properly. And believe me, it will be pretty obvious if that happens.
This doesn’t mean you just have to randomly read a bunch of books and hope you find something. You could start with thinking what kind of cuisine you like and look for books from that culinary food culture - such as The Queens of New York for Chinese food. Or, you could decide to focus on a time period, and try something from then, such as making marchpane (a bit like marzipan) from Romeo & Juliet. And don’t forget, there’s a whole genre of culinary detective fiction, such as Inspector Pamplemousse - as well as the Nero Wolf mysteries which, though not culinary, talk about food at length.
Of course, if you desperately want to make brownies, try googling “book that mentions brownies being eaten.” You have to be this specific in order to avoid books about the mythological figures.
Nick Hornby and Zadie Smith (particularly N.W. and White Teeth) - it feels like their characters occupy the same space, but somehow keep missing each other.