Bratwurst and beer mac and cheese

Aux champignons et truffes; a clash of the classes.

No it is not. It is déclassé all the way.  

The beer is a new type, New Planet, very good by itself, but I must say that here its bitterness is concentrated. 

I prefer cream base over this, a velouté in chef's terms. The rest of this can be repaired with a cup of cream style sauce, additional cheese, anything sweet to counteract the bitterness. Just of nudge off the bitter will do. Maybe you'll like it. Some people like that hops-y side of beer. I find that bitter and this very much so. I'd rather have malt than hops, so far as balance between them in beer.