These may very well be my favorite Belgian style beers. I love the dark fruit notes and the dry finish. I love those same dark fruit notes (plum, fig, prune etc...) in bock beers as well. I've brewed a couple of these beers now and thought I would go over the style and my experiences with it.
BJCP 2015 Guidelines - Belgian Dubbel:
A deep reddish-copper, moderately
strong, malty, complex Trappist ale with rich malty flavors,
dark or dried fruit esters, and light alcohol blended together in
a malty presentation that still finishes fairly dry.
BJCP 2015 Guidelines - Belgian Dark Strong:
A dark, complex, very strong Belgian
ale with a delicious blend of malt richness, dark fruit flavors,
and spicy elements. Complex, rich, smooth and dangerous.
If you go on to read the individual attributes of each style you realize they are very similar other than alcohol strength. Both should finish dry, drier for Trappist versions and either may or may not have some spice to them. They both share the dark fruit and malty characteristics. This is why I chose to cover both styles in one post.
I brewed my first BDSA in February of this year. I did some internet style research where I came across this slide presentation by Gordon Strong called "Designing Great Belgian Dark Strong Ales". There was a lot of information in the slide show which is hosted on docslide at
http://docslide.us/documents/designing-great-belgian-dark-strong-ales.html. My take away was to design a beer that would be complex and malty with raisin, plum and possibly some cherry notes. Also to to control fermentation temps and re-yeast at bottle time to make sure the beer drys out.
Due to the cost of candi sugar ($7/lb) I chose to use specialty dark malts to gain the dark fruit notes I was looking for. I had some crystal 150 and special B laying around so those won the day. I was counting on the yeast to take care of the attenuation rather than worrying about using sugar to dry out the beer. Turns out my hunch was right, Wyeast Abbey II did the job and then some.
Belgian Dark Strong Recipe:
http://beersmithrecipes.com/viewrecipe/1250178?&doid=57cde81f6eeb7
This recipe turned out to be exactly what I wanted for this style of beer except for one issue, fusel alcohol. I'm not positive that's exactly what I'm tasting. It's definitely an alcohol taste but it could be the slight alcohol/ethanol that the yeast is purported to produce. I plan on sending this beer in to several competitions to find out. It's currently been aging for 7 months and according to the slide show these beers do best with 9+ months of age on them.
Regardless of the competition results I love this beer. The alcohol taste is not offensive and all the malty dark fruit goodness is there. It's very complex and I'll be making it every year with greater emphasis on fermentation temperature control.
I also plan to use the same recipe for a doppelbock. I'd love to see if those dark fruit notes carry through during a lager fermentation.
If I'm being a complete dumb-ass, let me know in the comments.
Cheers!