Back in the day, Doppelbock brewed as sustanence for Monks in German monastaries. The beer had a high starting gravity, but was fermented only to around a 4%abv, with a large amount of residual sugars (carbohydrates) that provide sustanence.
Earlier examples of doppelbock was generally much stronger than the common Dopplebocks available today, as the original recipes produced a brew that contained approximately 9% abv as compared to the 7% give or take that is found out there now. Except for one. Kloster Ettal Doppelbock (Curator) is actually brewed to its nearly thousand year old recipe, and it is delicious. Therefore, that is the Doppelbock that I like to put the time into recreating.
This Doppelbock has an OG of 23 Plato and 50 IBU's. It is also dark, and my research has determined that it is made with a Munich type malt. Maybe not the Munich that we are used to or can get, but something similar. Therefore, this recipe contains 100% Munich (Weyerman in this case, but any German Munich will do). I also us a double mash technique here, and 4 decoctions of 1/2 hour each. The goal is for a gravity of 23 plato or around 1.096 OG. Go to my blog for other recipes, as every winter I will brew at least one. There is a recipe there using 15 lbs Munich and 1 lb toasted Munich (Avangard) that I made slightly different that the one below.
Grain Bill: 21 lbs Light (6-8 L) Munich Malt of German Origin (Weyerman or equal)
A few ounces of rice hulls
Hops: 50 IBU's worth of a German Origin hops (Bittering)
1/2 oz pelletized Hallertau, Tettnanger, Spalt, or other German hop(1st runnings)
1 oz pelletized Hallertau, Tettnanger, Spalt, or other German hop(flavor)
Irish Moss or other clarifier : 15 minutes left in boil
White Labs German Bock Yeast, with active and robust starter, works very well. I re-pitch the active yeast from a transferred Dunkel for this so as to get an aggressive start.
Mash in usung 11 lbs of Munich Malt at 120F and hold for 10-15 minutes (dough-in, use just enough water to wet the grains)
Raise temperature slowly up to 155 F using remaining water and hold until conversion is complete. I do this in steps, where there is a rest in between where I take a temperature measurement, and hold for 5-10 minutes before adding more water to get the temperature up to 155. Let sit for 20 minutes, then pull of 1/4 of the mash and put it in another pot. Boil for 30 minutes, then add back to main mash tun. There will be a little temperature loss during this time, but the boiling mash will bring it back up. Let sit, preferably between 155 and 160 for 10 minutes, then repeat while getting the sparge water ready. After the second 30 minute decoction has been added back, finish raising the temperature to around 170F. Sparge and collect around 1.5 gallons of wort (first runnings) in the brew kettle. Now switch to collecting the remaining run off into another pot. Take the brew kettle and place it on a burner, adding 1/2 oz of German hops. Let this boil until second mash is ready.
When enough wort has been collected to mash in a second time, heat up this liquid to strike temperature (around 170F) and mash in again (10 lbs of Munich, and rice hulls to prevent stuck run-off). Repeat the first mash procedure, doughing in at 120F, slowly raising to 155F and doing 2 additional 30 minute decoctions. Sparge normally, collecting into the pot that was previously on the burner, boiling the first runnings. Collect enough wort to fill the kettle up to the usual level for a single mash (about six gallons total).
Boil for 15 minutes, then add bittering hops. Boil for 75 minutes and add irish moss or clarifying pellet. Boil another 5 minutes and add the cooling coil to the pot for sanitization, along with the flavor hops. Boil 10 more minutes, cool and transfer to carboy. Aerate (we use a stone). Pitch the starter.
Fermentation usually takes about 3 weeks, give or take depending on temperature. The colder the longer, but the less lagering time that will be required later. When the fermentation is winding down, let stand at 60F for 2 days (Diacetyl rest). Transfer to secondary at this time and let sit another week, cold, where the fermentation took place. My method is to bottle at this time with one and a quarter cups of malt extract (DME). Bottle a couple smaller test bottles, and when the carbonation is full, place all bottles in a refrigerator as close to 32F as possible, or if there is another very cold space available, that works as well. 8 weeks of conditioning cold is recommended. Please note that I have not seen any sort of consistent pattern with fermentation times. Cold temperatures certainly will slow the whole process down. Be patient. Its worth the wait.
OG usually ends up in the 22-24 Plato range (1.092-1.100). I don' measure the final gravity, as I find it to be a waste of beer, but ABV will be in the 9% range.
1) Hops should all be German here for best results.
2) I am using water in the 70-100 ppm solids range.
3) Don't shy away from the Munich Malt. It works great, and plenty of color is created during the decoctions. It is the traditional way, and do not add any dark malt. The decoctions and the high gravity will make for a rather dark brew. Trust me. The hop character will not be as high as one would think, as there is lots of malt here to mask it.
4) Koster Ettal is available out there. Try some! It is delicious!