Re: the copyright thing, attribute any and all information you get from somewhere else. As far as mixing ethnic groupings goes, it’s fine, you can do anything you want. Just adding recipes for their own sakes is a little odd, unless there is an underlying food theme in the novel. Along that line, adding a vegetarian version really only is appropriate if their is a solid reason in the plot to do so. A family cookbook sounds like a better idea, if the focus is recipes. Are you planning to embark on a writing career? And, to answer the original Q, I have enjoyed some novels with recipes, a la Diane Mott Davidson.