1 12-oz bottle of dark beer, nut brown ale, or stout
1-3/4 cups white sugar (or half white, half brown sugat)
Combine beer and sugar in a saucepan over medium heat. Bring to a gentle simmer; cook, stirring occasionally and skimming off the foam, until reduced to a light syrup consistency, 30 to 45 minutes.
Note: I have read that this makes good mixer for an Old Fashioned, one part syrup to two parts bourbon, but haven’t tried it yet.