The brewers in Cologne (Köln), Germany have been brewing beer their own way for centuries. The modern version of Kölsch arose out of the brewer's needs directly after World War II as well as their desire to return to the simpler beer brewed by their predecessors. Lager brewing arrived much later in Cologne than the rest of Germany. It wasn't until the arrival of refrigeration that the style really took hold so the memory of their fathers' sales was fresh in the mind of the brewers. Using the older ale yeast with modern brewing methods, including refrigeration, the brewers developed their so-called hybrid beer style.
The way that Kölsch is served is almost as important as the way it is brewed. Köbes serve the beer in stages that are carried in specially made carriers. Okay, a little clarification–Köbes are the traditionally male servers that work the pubs in Cologne. Their very specific uniforms consist of long blue linen aprons, plain white or blue shirts, and a leather money purse. They are famously direct, perhaps even rude. They only serve Kölsch so it doesn't help to ask for any other kind of beer. The changes are tall, narrow glasses that hold 200 ML of beer carried in the special carrier pictured above.
As a German beer style, Kölsch is brewed according to Reinheitsgebot so only barley, hops, water, and yeast are used. The ale yeast used, however, is unusual for a beer that is fermented like a lager. The cold temperatures give the style a dry quality while the ale yeast contributes some fruity and bread-like aromas and flavors not normally found in lagers.
Kölsch is a study in subtle. As an ale, it has broad, sweet flavors. The lagering process keeps these flavors in severe check and contributes a dry quality that, while not as snappy as proper lagers, sets Kölsch apart from other ales. Its subtle flavors, moderate alcohol, and traditionally small serving size make this style a great session beer.
The agreeable nature of Kölsch means that is will get along well with many foods. The real challenge with this style is to pick a dish that won't overwhelm it. Simple foods like cheese and sausage make great companions for this German ale.