I'm not Italian, but I'm willing to give the OP the benefit of the doubt in the following way:
Have you ever read a professional cookbook ? I (would like to) think that what the OP was saying is that "hardest" level would equate to professional cookbook instructions.
In other words, if you were to look at a professional recipe for Lasagne, it would simply list "n ml Bechamel" as an ingredient and the recipe would simply state "layer using the Bechamel".
i.e. it would not list out the Bechamel ingredients, and nor would it tell you how to make it. The professional cookbook considers that you are reading a recipe for Lasagne. And that as a professional cook, you already know how to make a Bechamel (or already have some in the fridge from your prep). Professional cookbooks do the same for stocks and other preparations such as crème pat.