In a large blender cup, add ice, sugar cubes, creme de cacao, vanilla extract (optional), and the cream or Half & Half. Mix for no more than 5-10 seconds. Then add the alcoholic beverages in no particular order, then hit the frappe or whip button on the blender for 15-20 seconds, or until you can see that all the ingredients are well-blended, but before you over-blend and start the ice melting too fast. Serve in a tall pre-chilled Tom Collins or similar tall iced-tea glass. No garnish required, serve with a large-diameter straw.