In the world of ales, there are few richer and more complex examples than the strong, dark dubbels and quadrupels of Belgium. These dusky delights meld together a dense mélange of dark fruit, spice, toffee and toasted malt and alcohol warmth worthy of a tulip glass or chalice. They are contemplative sippers, to be sure. But in the Belgian tradition of drinkability, they are light enough that they won't weigh you down by the end of the glass.

Dubbel and quadrupel — also known as strong dark ale — are part of the Belgian monastic tradition of Trappist and abbey breweries, a tradition going back to at least the 6th century, when St. Benedict of Nursia wrote a book of precepts, known as the Rule of St. Benedict, that spells out guidelines for every aspect of monastic life. Two of the most important precepts involve work and hospitality.

Monasteries were required to be self-sustaining, so they needed an industry to support themselves. They were also important stops for weary travelers. Like inns, they offered rest and repast. At that time water could spread disease, but since brewing involves boiling, beer was safe to consume. Thus, beer brewing became an important industry for many monasteries. Among the best known of the beer-brewing Benedictines are the Trappists.

Few words evoke greater reverence in beer aficionados than "Trappist," a mark of monastic provenance that to many elevates these beers above the rest. It is virtually synonymous with quality and complexity.

But what does the Trappist designation really mean? The term "Authentic Trappist Product," along with the hexagonal label that signifies it, is a registered international trademark controlled by the International Trappist Association (ITA) in Vleteren, Belgium. Its website lists 12 monasteries whose beers currently bear the label.

The ITA has well defined criteria for determining which monasteries can use the Authentic Trappist label. The beer must be made within the walls of or in the vicinity of the monastery. The monastic community must control the policies of the brewery, provide the means of production and conduct business in accordance with a monastic way of life. Finally, the profits must be used to support the monastery and social services in the surrounding community. And of course, quality is important, as well.

The tradition of 'abbey beer'

So-called "abbey beers" are also part of the Belgian monastic brewing tradition. It's a loose term applied to breweries that are somehow connected to a monastery. It might be a brewery that makes or has made beer for a monastery under contract. It might also be a brewery housed on the grounds of a former monastery or that has simply taken the name of one. Other breweries with no monastic connection also brew the monastic beer styles.

It's a constant question why dubbel and quadrupel, along with their golden cousin tripel, are named such. The best explanation I've heard comes from the website of the Trappist Westmalle brewery. It says that each of these styles incorporates two, three and four times the amount of ingredients used to make the daily table beer of the monks.

The monks of Westmalle began brewing its dubbel in the 1920s, and theirs is still a style benchmark. Pouring a deep, dark brown, Westmalle Dubbel is a malt-forward beer that leads with toasted bread crust, toffee and hints of dark chocolate. Yeast-derived fruit and spice bring background notes of dried dark cherries, dates, black pepper and herbs that merge well with the malt. Moderate sweetness mid-palate fades into a dry and bitter finish.

Chimay Première, also called Chimay Red for its red label, was first brewed at Notre Dame de Scourmont Abbey in 1862. It presents a perfect balance of toasted grain and dried dark fruits, like prunes and dates. A trace of herbal hops and minerality add a savory note. The bone-dry finish is enhanced by just a touch of roasted malt.

Trappistes Rochefort 6 is brewed at the Cistercian Abbey of Notre-Dame de Saint-Rémy in Rochefort, Belgium. This one leans slightly toward the fermentation fruit. Prune, plum, cherry and raisin are the main event, with toasted bread crust malt in firm support. Light, lemony highlights that are unusual for the style add a touch of brightness. Alcohol is pronounced for 7.5% — especially a Belgian 7.5%. But that doesn't detract from the overall enjoyment of this beer.

The St. Bernardus Brewery in Watou, Belgium, is a proper abbey brewery. From shortly after World War II until 1992, St. Bernardus brewed beer for the Abbey of St. Sixtus, known to beer aficionados for its sought-after Westvleteren 12 ale. St. Bernardus Prior 8 is the brewery's dubbel. It's rich and malty. with notes of dark bread and a strong toasted grain character. Dried dark fruits give a bit of sweetness upfront that gives way to a dry, bitter finish. Raisin, dates and prune linger long after swallowing.

Quadrupels, the holy grail of ales

Belgian strong dark ale, often called quadrupel, is perhaps the grandest expression of the Belgian brewing art. These are big, warming beers with alcohol ranging from 8% to 12% and sometimes even higher. But that Belgian drinkability leaves them feeling lighter than they are. The range of flavors is vast, including toffee, dark sugar and caramel to chocolate, cherries and dark fruits.

Trappistes Rochefort 10 is a rich, full-bodied beer that leads with brown sugar, molasses and toasted grain. Dried cherries, raisin and semisweet chocolate blend in to weave an extraordinarily complex flavor tapestry. A sweet palate gives way to a dry finish. There is a lot going on in this beer, but it remains oh, so easy to drink.

I call La Trappe Quadrupel candy in a glass. Rich, sweet caramel malt and dark fruits mingle with vanilla, cinnamon and cotton candy sugar. Bitterness is restrained and hop flavor is minimal. A good touch of the characteristic Belgian yeasty fruit and spice sends this one over the top. Big, bold and warming, yet light and easy drinking for its heft.

With the first sip of Straffe Hendrik Quadrupel Ale 11° from De Halve Maan in Brugge, Belgium, I said, "WOW!" This beer is an intensely rich and complex palate-ful. Stewed prunes, dark chocolate, burnt caramel, dark cherries, brown sugar, toffee and raisins. It's all there. Notes of raisin come in as it warms and linger long into the off-dry finish. It's a contemplation-worthy sipper.

Het Anker Brewery's Gouden Carolus Cuvée van de Kaiser is another beer to take your time with. This one features all the dark fruits — figs, plums, prunes, raisins and dark cherries. It has an almost thick, concentrated fruit sweetness that dries significantly in the finish. Burnt caramel and a hint of dark chocolate add to its depth. This beer would be great to drink with dark chocolate truffles.

Brasserie St. Feuillien is one of several abbey breweries that had disappeared from this market but are now making a return. Though still 11% alcohol, St. Feuillien Quadrupel is a bit lighter than most. Dark dried fruits and candied plums are in the forefront. Soft, toasted-grain and caramel malt provide a base. Dark cherries linger into a very dry finish.

Next month: Exploring the centuries-old tradition of spontaneously fermented Belgian sour beers.

Michael Agnew is a certified cicerone (beer-world version of sommelier) and owner of A Perfect Pint. He conducts private and corporate beer tasting events in the Twin Cities, and can be reached at michael@aperfectpint.net.