The recipe is tailored for a 15.5 gallon keg kettle (keggle, keg with the top cut out), 15.5g potstill and a couple 18+ gallon fermenters. You can scale it down to whatever your setup allows.
I like to do this recipe 40 lbs (18kg) of malt at a time, for a couple reasons. 1) 15 gallons (57l) of strike water for mashing fits perfect in a half barrel (15.5g) keggle. 2) It gives 2 10 gallon runs, perfect for a half barrel still. It works equally well with Wheat malt or Barley Malt. My preference is 100% Red Wheat Malt, really nice flavors. But traditional single malt whiskeys are nice too, especially if 25% of the malt is replaced with peat smoked malt for a scotch style recipe. Beechwood and Cherry wood smoked malts are also available at some homebrew shops and online. They are nice but very strong, use sparingly.
Ingredients: 23 gal water (87l)
4 tsp gypsum
40 lbs (18 kg) milled Wheat or Barley Malt
Mashing and Fermenting:Bring 15 gal of the water, and gypsum to 160 degrees F (71C) (strike temp).
Put 20 lbs (9kg) milled malt in each of 2 20 gallon (75l) fermenters, or all 40 lbs in a bigger barrel if you have a 30+ gallon (113l) barrel.
Stir in half the water into each fermenter (7.5g, 33l) Temp should settle at 148F (64C)
Put the lids loosely on, and wrap the barrels up tight in blankets to hold the mash temp. Stir every 15-30 minutes.
After a couple hours remove the blankets and point a fan at the barrels, it helps cool them much faster to pitch temp.
When the temp is below 80F (27C), add 4 more gallons (15l) water per barrel (8g total), and take a large spoon or mash paddle and whip the mash up to a froth to aerate it well.
Pitch your favorite yeast. (Ferment on the grain) I use US-05 ale yeast, its high attenuation (ferments out dry) and tastes great. Be careful with temp, ale yeasts are best at 68F. Bakers at 80F. Use 2 packets per barrel, 4 packets total. Or 1 packet per 5 gal.
Distilling:After its done fermenting (1-2 weeks depending on temp)
Pull 5 gallons (19l) of the clear liquid off the top of each barrel, for a 10 gallon stripping run. (save and freeze the backset after distilling in ziplocks for next time
Squeeze 5 more gallons each from the goo in each barrel and let it sit and clear overnight, to run another 10 gallon wash the next day. I use large nylon grain bag for this.
Combine the 2 stripping runs and do a slower spirit run.
Make your cuts to taste and age on oak as long as you can keep your mitts off it.
Yield from 40 lbs (18kg) malt is about 2.6 gallons (10l) 60% (avg)
before cuts. Do your cuts to your taste preference. I get about 1.4 gallons (5.3l) 67%, after cuts. For $48 (US) 50 lb bag of wheat malt this works out conveniently to about a case (12 bottles) of 80 proof, at $3.34 per 80 proof fifth. For barley 20% lower cost.
EDIT: If you want to scale this down, use 2 lbs malt per gallon water. Thats typical, and you dont need to seperate the 2 water additions like above. I did that to fit a 15 gal cooker and 40 lb malt bill. Convenient for those of us using kegs for cookers and stills. Also the mash water addition calculation is easy this way...
if your grain is 70F, then the strike water needs to be 156 to hit a mash temp of 148 for 2lbs/gal mash. Doesnt matter if you do 5 lbs, 20 or 200. If your grain is not 70F or you want to go higher or lower on the malt/water ratio use this calculator
http://www.brewersfriend.com/mash/Enjoy, and cheers!