Beer Bread

What's going on here

Beer stands in for yeast here in a very literal sense — it already contains the carbon dioxide that a yeasted dough would spend an hour generating, produced during brewing rather than in your kitchen, so a beer-leavened batter needs the oven's heat but not any rest time to develop gas. Baking powder is doing the bulk of the actual lift, since most of beer's original carbonation has already partly dissipated by the time it's poured; the beer instead contributes flavour compounds from malted grain and hops, and its slight acidity, which helps the baking powder's second-stage reaction fire more readily in the oven. A darker, maltier beer gives a noticeably more pronounced flavour than a light lager, because more unfermented sugars and roasted grain character survive into the finished beer. Butter poured over the top before baking is a textural fix — it's a lean, low-fat batter, and that butter enriches just the crust into something closer to a savoury shortbread top.