Remove 3 quarts of the mash for the decoction, including a good mixture of both the grain and liquid. Add the Hallertauer hops to mixture and boil in a separate pot for 15 minutes. Stir frequently, and as foam rises to the top, skim and discard.
4.
Add the entire decoction back into the mash. In a separate container, heat 3.7 gallons of water to 185°F.
5.
After about 60 total minutes of mashing, mash-out by carefully pouring the 185°F water into the mash, stirring to equalize temperature to about 170°F.
6.
Slowly raise grain bag out of the liquid, allowing wort to drain from the grain. Hold grain bag above the kettle for 5 to 10 minutes as the wort drains.
7.
DO NOT BOIL. Cool the wort to under 80°F and transfer to a sanitized fermentation vessel.