I had one of these amazing beasts at the wonderful Kyoto Lounge bar yesterday. I shudder to think about how many calories were in the glass. But it tasted delicious. This was a pretty reasonable recreation. But the photo is of the original.
For one person you need:
1/4 cup maltesers
2/3 cup cold milk
1/2 cup chocolate ice cream
Place everything in a blender. Blend. Drink.