In this episode someone asked about diluting a high gravity beer to make one brew extend into two fermenters. Similar to macro beer's high gravity brewing, but they dilute on the way to packaging.
The minmum that i can brew, due to the location of the thermowell in my fermenter, is larger than my boil kettle. So, i am forced to either double batch or brew high gravity and dilute that single brew - or both. But, the mash tun is plenty large to make wort of higher gravity than anything i care to make, so a single high gravity brew is easy - compute the recipe in your brewing software as the full volume, then leave all of the ingredient quantities as is, but drop the mash water additions to fit the kettle, then adjust the hops to restore the BU estimates. While this boils, boil the volume of water that you removed from the mash water additions for at least 15 mins to sanitize. After the wort is chilled - through the counterflow chiller, if you are me - follow it with that boiled water, to chill it and flush the chiller.
It works a treat. Ive done this a few times with Schwarzbier and Pilsener.
More clues here: http://byo.com/bock/item/237-blending-f ... techniques
Prost,
Frank