Mix ingredients in a blender until smooth. Add more ice cream and reduce milk for thicker shake. Increase milk and reduce ice cream for thinner shake. For better favour, use porter ice cream.
It may sound odd, but it can be quite good. It is a staple at a pub I frequent. Porter is what makes this work the best, though stout is a viable substitute. I'm sure Lister would prefer it lager favoured. Still, where can you get Porter ice cream?