To anyone who argues that pizza is an <instance of:food> just ask them what toppings it has?
They will immediately acknowledge that pizza is a class of similar but distinct items. Just think about what statements you can make about an item and it will usually guide you quickly to what type of item you have.
Similarly the "Diary of Anne Frank" is an instance of a memoir or a literary work but is a subclass of book (because there are lots of physical books with that name). Literary works have authors and publishers. Books have numbers of pages and printers and physical locations.
This brings us to 'Chicago style deep dish pepperoni pizza'. Instance or class? The answer is that it is an instance of a 'recipe' with ingredients, cooking methods etc. and it is a subclass of pizza. There may even be a case to go to the 4 level model developed by the librarians at FRBR for books:
* Work - a literary work has properties like author, language,
* Expression - an edition of this work with a publisher, publication date, translator etc.
* Manifestation - is this the hardback, paperback or ebook, version of an expression?
* Item - a physical book with a purchase date, shelf position etc.
In practice Wikidata uses "edition" to mean both Expression and Manifestation and we often combine the edition and the work in one item, especially where there is only one edition of a work.
Translated into pizza
* Work = recipe. American Hot Italian style pepperoni pizza
* Expression = "Pizza Express" American Hot pizza
* Manifestation = Did you get the Eat in the restaurant or the take home from the supermarket version?
* Item = the pizza I ate last night.
OK?
Joe