After a long and mostly enjoyable quest, I think I have finally perfected it. Iced coffee so good that I don't feel I need to go any further. The secret, as it turns out, is coffee ice cubes. I made these with a batch of extra-strong coffee run through my filter machine the other day.
Into the blender goes one long shot of espresso, about the same amount of milk and as much sugar as you like. Put on the lid, but remove the center hole-thingy. With the blender running (at top speed), drop about 4 coffee ice cubes in through the hole, one at a time. Continue blending until you can't hear any more crunching.
Pour into a tall glass over (plain) ice.
Better than any crappy, fake, oversweetened excuse for iced coffee you can get anywhere.
Except maybe not better than a real shakerato in Italy - but then again, that could just be about being in Italy.