Ice cream has gone down many permutations and combinations in recent years. First, there was the molecular magic of nitro, using it to whip up savoury groups such as bacon and egg. Then there were cereal-milk-flavoured soft-serve, and hard shakes secure with liquor. Now lollies are getting a worldly twist. At San Sebastián’s Loco Polo, the shopper can build their own, select from bases such...