I’ve never heard anyone else say that except me, and now maybe my kids.
The faux-intellectual streak of Anglo-Saxon “nativist” English purism had at least one good feature: you probably didn’t abuse unrelated languages to express yourself.
What’s wrong with “with broth?”
Good strong Anglo-Saxon root words. 
“Au jus, please? And LOTS of it!” 
Jesus! What the Pope do you think happens at a bris?
I quoted the wrong part above. Obviously I’ve heard people say ah zhoo. It’s just the ‘ow juice’ that’s my own thing.
I’d go with “with au jus sauce”
BTW, most Americans (even those who know it’s an adjective) pronounce it “aw zhoo” rather than the more correct “oh zhoo”.
(Forgive me for not using the universal phonemes, whatever they might be! (Ignorance clung to, in this case. Yeah, they’re cool, but I have other fish to fry. Maybe someday.)
- where “aw” rhymes with “Mackinac”.
I don’t care what people call it, but boy, restaurants had better know its actual meaning and convey that in their wording on the menu.
Other than the sacrifice of a Christian baby to Moloch, just what I learned in nursery school at Temple Emmanu El. 
Like “sauce,” “juice,” “gravy,” and any number of other English words that people propose to use for this, it has other meanings, and a predominant meaning that is decidedly not the same as “au jus.” Markedly so in a restaurant context.
The real question is, what’s wrong with “au jus” as a noun phrase that refers to the substance in question? Nothing*, I would say.
*Except offending the sensibilities of some language tyrants, and they should just order the chicken and stay clear of the matter. 
Au jus makes as much sense as a la mode, just go with it. The problem is jus by itself has come to have a second culinary meaning (i.e.: red wine jus). An au jus is a thin beefy broth, often cheap and not made with actual beef. A jus is a thick, reduced, fancy sauce.
Well, I’ve just finished reading this whole thread and I have to say I now feel like a complete country bumpkin who knows nothing. 
Around here, we pronounce it “awe juice”.
…and I’ve just now with your post cottoned on to the fact that we say this word wrong too - we pronounce it “mack-in-ack”.
I’m so embarrassed. I think I’ll go climb back under my rock now.
Language is usage. If most people are using “au jus” as a noun phrase, then that’s what it is. How you feel about that is your own issue.
All words (and phrases) mean whatever we use them to mean. Dictionaries and grammars play catchup with usage; they are powerless to do anything else.
If using “au jus” as a noun offends you, then don’t do it. If my using it as a noun offends you, mind your own business.
It strikes me as similar to the way “au pair” is used as a noun phrase in English.
I’ll accept that when people start saying “octopuses,” and shut up already with the stupid non-word “octopi.” I’m all for making foreign words behave as English words, but I constantly butt up against idiocy like “octopi,” and even “feti,” for “fetuses,” so I am going to hold “au jus” hostage.
“Au” doesn’t mean exactly the same thing as “avec.” “Avec” is pretty much the same as “with,” but “au” is a contraction of “a le,” which in the phrase “au jus,” does translate to “with juice.” In “au pair,” it’s a French phrase that means “in exchange,” or “equal to,” because someone working as an au pair exchanges work for room and board, the chance to travel (and usually pocket money). So “sandwich with au jus” is redundant, but “the kids are with the au pair” isn’t. It would be pretty much the same phrase in French.
Isn’t it used as an adjectival phrase in French, though - “une/la fille au pair”?
Yes, but “avec la fille au pair” isn’t redundant, and in English, it was commonly “au pair girl.” Saying “au pair” and leaving off “girl” is an elliptical phrase.
I’m just saying it isn’t analogous to “au jus.”
That’s weird. I grew up in the UP & Wisconsin, and the pronunciation of things like Mackinac island and Sault Locks gave us a reason to laugh at newbie residents and tourists. Now I see Wikipedia calls them “Soo Locks.” Oy. I feel old.
Anyhoo (anyhault?), “with au jus” is like “and etc.” Drag your nails across my chalkboard while you’re at it, Mr. “Language is Dynamic.”
Now I am really wanting a french dip roast beast sandwich … with extra horseradish. sob