I suppose they wanted you to realise that "al" means "in the", so it's "chocolate in the cookie" = chocolate cookie. It took me a while to work out what it meant though, I was thinking 'I eat a chocolate in the cookie? That can't be right!'
I am talking about Spanish, but I think that in Italian is the same, for us it is not the same "biscotto al cioccolato" que "biscotto de cioccolato", the first one could be translated as "biscuit with chocolate" and the second as "chocolate biscuit", the first one could be a cookie covered with chocolate, the second one a brownie
No, the Dutch don't use the word 'cookie'; they say "koekje" or "biscuitje". There are many different types of cookies; I mention a few: sprits, zandkoekje, jan hagel, wafel, Arnhemse meisjes, Weesper moppen, speculaasjes. In the supermarkets In supermarket there is sometimes "cookies" on the packaging, but then there are indeed cookies that resemble American cookies inside. 'Cookie' is American English and 'biscuit' is British English. I prefer 'biscuit' as translation for 'biscotti'. It's an accepted translation.
If my command of the language is correct, a in italian means to, at or in depending on context. So al is the combination of a and il/la; it's like saying to the or at the, generally speaking. However, like many languages there are acceptions and different ways to express a thought. So cioccolato al caffè in this instance should mean chocolate coffee because it's like saying the chocolate resides in the coffee. Hope this helps
Also, con does mean with but more to do with pairs than combinations of things.
I think it's ridiculous that it counts it wrong when you type the English translation; the point of the exercise is to evaluate one's understanding of spoken Italian, and if one types the English translation of what they hear, it's clear that they understood what the voice said and have met the skill requirement for the exercise.