Originally Posted by HairyDogBrewing
Search for 'partigyle'.
If you're making a 'big' beer, use enough grain to get your gravity with first runnings.
Then sparge and use that to make a smaller beer.
If the second runnings are too thin you can add sugar or DME.
I've done this and the results are good, but I don't have a way to boil 2 batches at once.
Time is the deciding factor for me.
+1 it's called partigyle. It's an English brewing technique for getting the most out of the grain when making a higher gravity beer. You make a giant mash and use the first runnings for the high gravity batch and then the later runnings for a low gravity batch. Like a barley wine and a mild. The trick is both beers have the same grain bill.
A friend of mine did this recently and made 5 gallons of Belgian triple and then 5 gallons of pilsner from the same mash.