From Mr. Adams' website:
Samuel Adams® partnered Felchlin, a renowned Swiss chocolatier, to develop a unique innovation, Samuel Adams® Chocolate Bock. We started with a complex selection of carefully roasted malts combined with hand-selected Noble hops from Bavaria, the world’s oldest growing area. After using a centuries old brewing process, called Krausening, we slowly aged the beer on a bed of rare dark cocoa nibs from Felchlin®, a renowned Swiss chocolatier... The resulting beer, Samuel Adams® Chocolate Bock, has a big, malty character that is combined with the subtle sweetness of chocolate, giving this brew a complex full-body taste with a velvety finish.
Beer Advocate doesn't necessarily rave over it, and RateBeer is being mighty fussy for me right now.