I don't think you quite get my meaning yet. Viaggiatore indicates the imperative form for second person plural for mangiare is "mangia" ... seems to be the case here:
Also, this site shows the swap of the second and third person forms in imperative for 'are' verbs:
"the tu and voi forms are identical to their corresponding present indicative forms, except for the tu form of -are verbs, which add -a to the root: domandare > domanda" ...
So, the first part of the sentence appears to command you to eat ... I guess:
mangia! = eat!
(I'll bet that is common in Italy!)
... but, the second half of our sentence appears to be present tense for "you want".
"Mangia" is an imperative form, directed to "you". http://italian.about.com/library/weekly/aa011900a.htm
That's one of the alternatives it offered when I screwed it up. Maybe that added that because of your comment, though.
It's weird to make you lose over the translation of a speech element they haven't covered yet (imperative), especially when it could be translated using elements they have already covered.
Apparently, "Tu mangia!" is the imperative form of mangiare.
How many people does the sentence address? Mangia is formal for he, she or it eats. Vuoi is familiar for he, she or it eats. It sounds like the speaker is ordering person one to eat pasta whenever person two wants person one to eat pasta. Maybe this is a line from a movie scene in an Italian prison. I can't see ordering someone to eat as much as they want.
Two examples contradict each other. Here "Mangia la pasta quando vuoi": this is the 'tricky' irregular Italian imperative which is different from the 2nd person singular "mangi". Yet a little further down this exercise with "Eat as much pasta as you want" it suddenly has to be "mangi". Come on DL, some consistency please!