Think of a dubbel as a Belgian dark strong ale's laid back little brother. There's still a rich malt character complemented by the yeast's fruit and spice—and not an insignificant amount of alcohol—it's all just a little less intense in a dubbel. The beer style originated in monasteries in the Middle Ages, though the style reemerged as something close to a beer we'd recognize around 150 years ago.
A dubbel is a fantastic entry point for those not familiar with Belgian beer and an even better partner for food. The beer's characteristic aromas of plums, raisins, caramel, and warm bread are inviting; the brew is chewy and medium bodied, and it finishes dry and warming. It's a malt parade with a restrained bitterness keeping the whole thing in check.
Brewing your own dubbel is a good exercise in piecing together different specialty grains to create a complex yet coherent malt profile. Let's break down the beer's different elements.
Malt and Sugar
Steering away from the sugar-focused course taken with the Belgian dark strong ale, this dubbel relies more heavily on a variety of specialty malts than sugars to build layers of flavors. This appears to be a more "American" approach to brewing dubbel, as many Belgian brewers still rely on base malts and dark candi syrup.
The goal with this recipe is to have a greater focus on the beer's malt while maintaining complexity. Caramunich provides a dried cherry or plum note and Special B provides a raisin quality. Aromatic malt further enhances the beer's malt aroma. Chocolate malt, despite its name, is more about color adjustment than aroma or flavor. It helps give the beer its deep ruby hue, though it also contributes a slight roasted nuttiness. All told, specialty grains account for just over 15% of this recipe.
The majority of the grist is still made up of two-row Pilsner or pale malt along with a good dose of Munich malt to add a breadiness to the finished beer. Dark Belgian candi syrup will bring dark fruit flavors and aromas to the mix, but keep that addition to less than 8% or so of the recipe, so you don't boost the alcohol too high and thin the body out too much. I also like a pound of wheat malt to improve mouthfeel and head retention.
Once again, hops are relegated to a supporting role. Dubbels typically have a lone bittering addition before or at the beginning of the boil. I prefer a clean-bittering, high-alpha hop like Magnum, but the type is not critical, in my opinion. A few American dubbels are somewhat hoppier, but I wouldn't use more than a modest noble hop addition for flavor and aroma.
Healthy Belgian yeast is essential to achieving the right mix of phenolic spiciness and fruity esters found in a great Dubbel. My yeast of choice for this is the Westmalle strain (Wyeast 3787 or White Labs 530). I've found it to produce aromas of plum, stone fruit, and spice. Another solid choice is the Chimay strain (Wyeast 1214 or White Labs 500), which can be a bit subtler.
Regardless of which yeast you choose, pitch an adequate amount and provide the wort with plenty of oxygen before pitching to ensure a healthy fermentation. Make a yeast starter or buy multiple packs of yeast. I use Mr. Malty's Pitching Rate Calculator to determine how much yeast I'll need for a batch. For aeration, carefully shake the carboy back and forth for a few minutes prior to pitching the yeast or oxygenate for a minute or two with an oxygenation stone, if you have one.
Keep your temperature stabilized on the cool side (64°F to 66°F), especially in the beginning of fermentation. Otherwise, you could end up with a hot, solventy mess. I like to keep it cool for the first couple of days, which is when the majority of the ester profile is developed, then allow it to free rise on its own until fermentation is complete.
Dubbel is a beer style that will benefit from a little additional time to mellow, meld, and get awesome. So be patient, show restraint, and give it a while to condition in the fermentor and in the bottle.