> But, do professional chefs use cookbooks? -- I know the answer to this one. No, they don't. Or, not in the way they are intended.
> a book may give a general direction by saying that this or the other particular pastry traditionally uses lemon juice. And the chef would know how to ration it and how to work the dough.
This is exactly how cookbooks are intended.
A few decades ago there was a more popular genre of cookbook: a huge 200p book that would go to a newly wed wife so she gets better at cooking, and it would have half of it just explaining the basics: how to skin a chicken, how to cut vegetables, how to adjust an oven etc. And you'd go through all these basic training before trying the recipes, which had very terse instructions ("skin the fish, remove the bones, cook it meuniere style"). To me traditional cookbooks are just skipping the training section assuming you've already gone through it all.