Dark rum, coffee liqueur and Irish cream blended with cookies-and-cream ice cream. Five minutes, one blender. The glass goes in the freezer first.
Ice dilutes and thins the texture. The frozen glass does the chilling.
Longer and the fat breaks; you get a thin drink with foam on top.
Spiral syrup down the inside wall, then freeze it again while you blend.
Dark rum matches the coffee profile. Spiced rum deviates from it.
Vodka works just as well and lets the cocoa and coffee stand alone.