I'm on record in any number of venues saying that Altbier is the perfect beer style. Not only do I love brewing and drinking it for its showcase-like approach to featuring malt and hops in a highly-consumable (if not quite "session") strength, but I like that I can use it as a nearly-year-round "house" beer style. Once in a while, though, you want to push the envelope a bit more: celebrate a special occasion, commemorate an anniversary, show off at an event, etc. On those days, I'll reach for a recipe for a style that doesn't even exist in the BJCP Guidelines: the "Sticke" (or "secret") Altbier.
The 2015 revision added a panoply of IPA and Historical and other specialty styles, but strangely collapsed all Altbiers into one category (and, for that matter, indicated explicitly that sticke altbiers didn't belong in that category, without indicating where they should be entered - but I digress…). I guess there's always the good old "Experimental Beer" sub-category, but it feels odd in a style with such a long history.
You'll have to hunt down your own category for entry, but one thing you won't need to do is wonder why you brewed this style in the first place. It takes everything I love about the Altbier and turns up the volume, and while that's not really something you need every day it certainly makes for a great change of pace!
Albtiers in general are amber hybrid beers. Orange to copper in color, they are neither truly ales nor truly lagers, and instead have elements of both (regardless of the yeast strain used). They ferment cool but not cold in order to add a touch of fermentation character (usually a berry/cherry ester). They're also complex in their malt profile - though not sweet - with a range of bready base and crystal malt flavors, and a bit of chocolate malt to dry out the finish. Hops play a significant role, too, with firm bitterness but often less-robust hops flavors.
When we make the leap to Sticke Alt, there are some noticeable changes. First, our color will generally deepen, which is a reflection of the increased poundage in the grist to yield about 1.25 points more in ABV. Second, hops aroma and flavor are both increasing; bitterness is, too, but it's mainly preserving the same bittering unit to gravity unit ratio. Third - and this can be the tricky part - the crystal malt additions are getting bigger and darker. The reason I point out that challenge is because although we want a more robust punch from the malts, we still need a beer that finishes "surprisingly" dry.
Ultimately, Sticke Alt should be recognizable as an Altbier, but louder.
The good news here is that my standard Altbier is already pushing to the upper end of its own style, so if you've made that one (and if not, why not?), you're already practiced in the overall strategy. The recipes, though, do have some differences.
First, we're increasing base gravity while also switching up the proportion of Maris to Pilsner malts. Start with six pounds of Maris Otter and keep the same four pounds of Pilsner malt. Add 1.5 pounds of Munich malt (again, a slight increase). Finally, we're adding four ounces of pale chocolate (no change there), half a pound of Caramunich (double the Altbier recipe), and a quarter-pound of British 90L crystal malt. One reason the pale chocolate addition can stay steady is that British dark crystal has some light roasted character in addition to a complex toffee-and-biscuit flavor, and it's a great fit for this recipe.
Increase bittering hops to 40 IBUs at 60 minutes (a little over two ounces of Tettnang should do it), then add a full ounce of Tett at 15 minutes remaining to give yourself a more-prominent German floral hops flavor and some additional IBUs. Finally, in whirlpool or at flameout you can add half an ounce of Hallertau Mittelfruh to punch up the aromatics.
This beer will be fermented with the Wyeast 1007 (German Ale) yeast, just like the standard Altbier, and for the same reasons: perfect ester profile, full attenuation, and I usually have it sitting in the fridge.
Attenuation matters in a 5.5% ABV Altbier. It matters even more in a 6.7% Sticke Alt (and just wait until we get to the Doppelsticke!). Mash at 152F for 75 minutes (the additional time will create a slightly more-fermentable wort), then boil, chill, and pitch as usual. Start fermentation a little lower (58F) at the start, then after 72 hours increase to 60F, then increase by one degree per day for the next ten days. We want to ramp up temperature to promote active fermentation right through completion - once you're at 70F, let it sit for an additional two weeks (or, obviously, until a few days after the completion of visible fermentation, whichever is later).
Go ahead and cold-crash before packaging to get a little head start on clarity, but you'll be lagering this beer for a few weeks before consumption. Carbonate to two volumes of CO2 - no need to make it too spritzy!
The one flexible item on this one is hopping. I find the 1.5 ounces of late hops to be plenty to add a just-higher-than-moderate level of hops aroma and flavor, but the malt backbone here can hold up to a lot more, both in terms of flavor and bittering. Feel free to increase at will! Prost.