Thanks for the hard cider link--good stuff.

Because it was traditionally done with hard cider, this seems like a good place to mention "jacking," which is the name for increasing the alcohol concentration by partial freezing.

Basically, you just leave a barrel of cider out overnight after the weather starts to fall below freezing, the pitch out whatever ice forms on the top. Because the freezing point of water is much higher than that of alcohol, the ice will be almost entirely water, so that the remaining beverage will have a higher alcohol content. (This also concentrates pretty much everything else in the beverage, including any remaining sugar and other chemicals that give it its flavor.)

You can repeat the process several times, getting your cider a little harder each time. Just do some "quality control" each time and bring it in once you get it the way you want it.

As far as I know, concentrating the alcohol through jacking is legal. It's also free if you live somewhere where the overnight temperatures fall below freezing, and uses a lot less energy than running a still.