Mill the grains and mash in at about 36–38 °C.

First decoction: Pull about one-third of the mash from the thickest part, bring it to 70–75 °C, and rest there for 10–35 minutes. Bring the decoction to a boil, boil it for 5–15 minutes, then return it to the main mash, which should rise to a temperature of 45–50 °C. Rest for 5–10 minutes.
Second decoction: Again, pull a thick one-third of the mash, bring it to a boil, and boil it for 20–50 minutes. Return it to the main mash, which should then rise to 60–65 °C.
Third decoction: Pull 40 to 50 percent of the mash, but this time from the thinner, more liquid portion. Boil it until the protein coagulates and a hot break forms and settles, then return it to the main mash, which should rise to about 75 °C. Lauter and sparge to get about 26 liters of wort, or more, depending on your rate of evaporation.

Tailored to modern ingredients and methods:
There are two decoctions instead of three.
For the first decoction, pull a thick two-thirds of the mash, instead of one-third, with a 20-minute rest at 70–72 °C, then boil for 10 minutes before returning it to the main mash, which should bring it to about 65 °C.
Boil for 90 minutes instead of 2 hours. (W-034/70 works at 18-20 °C as well, but need 1 pck instead of 2.)

Inspired by traditional vienna lager recipe see bellow