Pluralizing Noun Phrase?

Question regarding plurals: Let's say I own a restaurant, and each day I feature two new soups. Are these soups called soups of the day? or soup of the days?

Then, let us say my restaurant only features one soup of the day, and I need two bowls of it... do I also call "please get me two soups of the day"? Would I then get a snarky remark from some college bound cook that we only feature one soup of the day?

Please help clarify, and note that I am most familiar with the Chicago Manual of Style

If a noun is modified in creating a noun phrase, you pluralise the noun hence:

Courts-martial

Happy hours

Passsersby

Daughters-in-law

Two-head nouns have both nouns pluralised if the plural of the first is irregular, but only the second otherwise:

Menservants

City-states

Longer compounds will sometimes though begin to be considered as a single unit, leading them to be pluralised as such. Hence you can find both "jack-in-the-boxes" and "jacks-in-the-box" and both "pastramis on rye" and "pastrami on ryes" (and potentially hedging the issue with "pastrami-on-rye sandwiches".

This could conceivably apply to "soup of the day", and so one could indeed find "soup of the days". It is though generally still considered as a produced phrase understood by parsing each word, rather than as a unit. As such while I wouldn't be amazed to find "soup of the days" I'd still recommend "soups of the day".

The first would be soups of the day. soup of the days sounds like a single soup for multiple days, although I don't think I've ever heard of such a thing (even if you had the same soup on two days, there's not much point in grouping them).

If you want two bowls of today's soup, it would be two orders of the soup of the day or two bowls of the soup of the day. If you said two soups of the day you would be understood, but it doesn't seem as natural.