I was just discussing this with a friend who has an extensive knowledge of copyright law, intellectual property, public domain, etc. A recipe is one of the few things out there that can’t really be copyrighted. Every time I follow a recipe, whether I change it up or not, the end result is something that I have produced, so I can post that list of ingredients onto my blog and technically wouldn’t have to attribute it to anybody.
The conversation didn’t get to the method, but I agree with Marlene that you can’t just copy word for word what someone else has written for the technique, since it’s an author’s own words and would probably be on par with quoting entire paragraphs from published novels. Credit is necessary for things like that.
As for ethics, this is all my own opinion now, it seems wrong that his intent is to just take an entire collection of recipes (from one source? one person? or various sources?) and make them “his”. Where’s the creativity and originality? What’s his personal connection to these recipes that he wants to place them all together into “his own” collection? I’m sure (at least I hope) it’s more complicated than just copying a bunch of recipes for the sake of publishing a book, but for now it seems a bit sketch.