French term (edited): Gratiné de volaille à l\'époisses

I agree that normally I would reverse the word order, IF it were only a single ingredient: chicken gratin
BUT with the second ingredient here, I find that can get clumsy, or/and can occasionally even become misleading (if the second ingredient starts to look like a mere accompaniment.

In this case, however, I'd be inclined to add the 'cheese' — anyone not in the know could be forgiven for not being familiar with this particular product (unlike say Brie or Camembert), but as dairy products are a common source of food intolerances and allergies, it is probably helpful to the EN-speaking diner to point that out, instead of leaving them to ask the waiter or having a potentially unpleasant surprise.

Note of course that 'volaille' isn't necessarily automatically 'chicken' — but we would rarely if ever say 'poultry' on a menu in EN, and so 'chicken' is a reasnoable bet — though it would be wisest to check all the same with the chef. Sometimes it is a cover-up for using cheaper turkey meat...

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Note added at 12 heures (2017-06-10 11:00:08 GMT)
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I emphasize again that 'volaille' is USUALLY chicken in a FR menu; almost invariably, if it is any other fowl (or rabbit!), they will want to vaunt that fact. Equally, it's relatively uncommon to find 'poulet' mentioned as such, unless it is as 'poulette' or 'poularde' or 'coq' or 'chapon' or somesuch. Neither have I ever come across 'poulet' and 'volaille' on the same menu, which would of course tend to suggest some distinction was being made between them.

The executive catering manager at one of my customers, a renowned major hotel chain, said that when translating their menus, I could take it for granted that by default 'volaille' was intended to mean 'chicken' unless specifically indicated to the contrary; usually, if it is duck etc. the restaurant is only too pleased to vaunt the fact. The only real problem arises in those thankfully rare instances where 'volaile' is being used as a non-specific way of hiding the fact that cheaper turkey meat (almost always) has been used, which is not going to be very noticeable if it's cut up and in a dish with sauce, for example.
The only other exception I've personally ever come across is with the basic ingredient 'gésiers de volaille (émincés)' where, if you check the packaging, you usually find they are in fact turkey — understandably, inasmuch as turkey gésiers are a bit bigger than chicken ones!

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Note added at 13 jours (2017-06-23 05:29:36 GMT) Post-grading
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I entirely take Marlen's point about 'trendy' descriptions of dishes on menus — and indeed, a similar trend is very much evident in EN. However, generally speaking; FR menus if translated too literally tend to sound over-flowery and pretentious in EN.
But in any event, if we assume that the EN 'translation' is deemed necessary / advisable for the benefit of customers who may be less accustomed to FR culinary descriptions, it seems to me that the function of the EN is to explain whatthe customer can expect to find on their plate — and above all, to not give them a false expectation of things they will NOT find.
It is rarely possible (and arguably unhelpful) to find an equally flowery description in the EN version. When I am translating menus for upgrade establishments of the ilk of Le Meurice etc., I always discuss with the Maître d'hôtel and the chef just how they would like me to proceed.