title_body: What is the result of boiling beer?
upvoted_answer: Well, I never tried such an heresy, but theoretically you will end up with some kind of syrup (or broth, I really don't know the most appropriate word in english for it), thick, and more or less sweet depending on the beer you use. Some beers have more residual sugars than other ones.
  
  Alcohol will be the first to evaporate, then water, which is basically the majority of beers composition, in volume, leaving behind sugars and proteins, basically. Those last compounds can be modified or merged, as well, I can't say. Then, depending on the beer's malt bill (pale, crystal, caramelized, roasted, smoked, etc), you might get different flavors related to it. I don't know what would happen to hop compounds when boiled for a long time, but you'll probably still get some bitterness from them.
  
  You know what, you question got me curious about how it would taste at the end. =P