Originating from Belgian monastic brewing traditions of the Middle Ages, abbey dubbel ales are now produced by many secular commercial breweries in addition to some of the "authentic" Trappist (real Belgian monasteries) brewers. The dubbel is a double fermented ale that is dark amber to brown in color with a long lasting dense head. Dubbels often have low bitterness and reveal rich malt flavors of dark fruits, dry fruits, chocolate, nuts, and caramel. Yeast aromas and flavors are common along with the imprints of their fruity ester (banana perhaps most common) and spicey byproducts of fermentation. Like other Belgian-styled ales, candi sugar is normally used to produce a dubbel. Abbey dubbels overlap some examples of both dark Belgian ales and strong ales in maltiness, complexity, and alcohol strength, normally nestled right in between the two.