The cream that is used for the original recipe has been cold steeped with bran, giving it a thicker than usual consistency. Stirring in the cream changes...
You wonder - why garnish with raisins? Then you taste it and you understand. A sweet, raisiny flavor, and the float of half-n-half is nice (but I think it is optional, and likely should be reduced to 1/2 oz if used). Very interesting combination of ingredients that combine very nicely - not a typical genever cocktail.