When we were in Okinawa researching just what it was they ate that helped them all live to be 100, we discovered the delicately floral-flavoured Okinawan sweet potato ice cream, famous throughout Japan. It is made from the equally celebrated Okinawan sweet potato, a deep purple-coloured tuber believed to have miraculous nourishment properties. Even though I am not a big fan of strictly following recipes, when the Times in the UK asked me to come up with a top ten list of some of my favourite Japanese recipes , I knew the sweet potato ice cream had to be on it, so I set to work to figure it out. I think this is pretty much an exact match for the light, non-eggy way the Okinawans like to eat their ice cream. Ordinary sweet potatoes work almost as well, although you won’t get quite the same pale lavender colour.
(0 out of 10 for presentation, perhaps, but it tastes fantastic).
150-200g baked, blended and sieved sweet potato flesh
500ml whole milk
2 tablespoons cornstarch
30g mild honey
Seeds of half a vanilla pod
Essentially, all you are doing is replacing the fruit puree element of your favourite fruit flavoured ice cream recipe with cooked – baking best cuts down their water content and intensifies flavour – blended sweet potato that has been pushed through a drum sieve. In this case I use a basic gelato recipe because I find egg-based ice creams can taste, well, eggy. Mix a little of the milk with the cornstarch to make a slurry. Heat the rest of the milk along with the sugar, vanilla seeds and sweet potato pulp until they almost boil, mixing well. Reduce the heat and add the cornstarch slurry, stirring constantly for a couple of minutes until the it all thickens nicely enough to coat the back of your spoon, like grandma used to show you when making custard. Off the heat, add the honey and stir. Cool thoroughly, and then pour it into your ice cream maker as per usual. I have made this ice cream without the sugar and vanilla in the past and it was still good, just make sure you use a light, mild flavoured honey. A little lime zest also works well to cut through the chestnutty sweetness.
Think it's time I got a new ice cream machine, don't you?