It's very important to be careful here, and you need in particualr to check out US food labelling regulations to check, but there is sometimes a difference between 'made with cocoa' and 'flavored with cocoa' and 'cocoa-flavored'.
Certainly 'au cacao' implies it does actually contain some.
Do check this very carefully, in order to avoid giving a false description.

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Note added at 12 hrs (2021-01-12 09:18:56 GMT)
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It would actually help us if you gave the original source text in EN.

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Note added at 1 day 18 hrs (2021-01-13 16:15:44 GMT)
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If your waiter were inviting you to choose which flavour ice-cream you'd like, they'd probably ask « Quel parfum désirez-vous ? » — I don't believe they'd ever say 'arôme'; but if you buy crisps, they may well be labelled 'arôme fromage' etc. — 'cheese flavoured'.

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Note added at 2 days 12 hrs (2021-01-14 09:24:12 GMT)
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As someone else has said, it is rather unusual in FR (not to say EN!) to say something is 'cocoa-flavoured' instead of 'chocolate' — unless they are seeking to emphasize the fact it is truly non-dairy?