Please be aware that I'm neither a native English speaker nor a teacher.
+1 for Pistachio gelato.
Back to the implied verb, I don't agree there necessarily is one. Think of the accusative case in Latin and Greek, which (sort of) lives on in our translations of the Classics... e.g. "O, Agamemnon!" or even "O, Canada".
To me, "you fool" is something we might compare to an accusative case of the noun 'fool' -- without a verb.
As for the initial question by the reader from HK, I'd explain it to my kid as follows.
In Cantonese, you can call somebody a 'cute' insult either with an accusative type noun, or with a complete sentence, interchangeably:
"Ham sap lo!" cf. "Lei hai ham sap lo!"
"Soo zai!" cf. "Lei hai soo zai!"
[Sorry, my keyboard can't type Chinese at the moment]
Meanwhile, back on topic...
Nope. C'est un flic blond - pure ignorance. Spanish isn't my strong point.