Daigaku imo and black sesame caramel ice cream

Method

• step 1

  To make the caramel, put a non-stick baking mat or baking paper inside a shallow tray. Put the sugar in a heavy pan over a medium-low heat, gently heating until melted and turning a golden caramel colour. Carefully add 1 tbsp of water (it will spit), mix well, then add the sesame seeds and stir until thoroughly combined. Pour the mixture onto the baking mat and leave it to cool and harden.

• step 2

  To make the ice cream, heat the cream and milk in a large pan until steaming. Meanwhile, whisk the eggs, yolks and sugar in a large bowl with electric beaters until whitened and ribbons appear. Pour a third of the cream mixture into the eggs and mix well until completely combined.

• step 3

  Pour this into the pan with the remaining cream mixture and cook over a low heat, stirring and scraping with a spatula for 5 minutes until a coating consistency is achieved and a line remains clear as it is drawn on the back of the spatula. Turn off the heat, transfer to a lidded plastic container and let the mixture cool down. Meanwhile, break up the black sesame caramel into small pieces, then crush them into rubble using a food processor or pestle and mortar. Add the rubble to the cold custard, cover and refrigerate for at least 2 hours or preferably 24 hours. Pour this mixture into an ice cream maker and churn until frozen – this will take about 45 minutes. Put the ice cream in an airtight container and freeze until needed.

• step 4

  Peel the sweet potatoes, leaving some unpeeled if you like a more textured presentation. Cut into 3cm pieces of various shapes, wash them in water, drain, then put them in a pan of cold water over a medium-high heat. Bring to a boil then simmer for 8 minutes until nearly cooked through.

• step 5

  Drain the potatoes, then put them in a roasting tray and leave them to air dry for a few minutes. Give the tray a shake to chuff them up – this opens up fissures in the surface which will help make them crispy and golden. Allow them to air-dry and cool overnight (or for at least 6 hours), uncovered, in the fridge to remove moisture.

• step 6

  Fill a pan no more than a third full with oil and heat to 140C or until a cube of bread browns in 1 minute. Fry the potatoes for 5 minutes until cooked through but only very lightly coloured. Remove the potatoes, air-dry until cold again, then refrigerate uncovered for 6 hours or overnight.

• step 7

  Make the sauce by gently heating the sugar, honey, vinegar and 2 tbsp of water in a pan until the sugar has melted, then increase the heat until a light caramel is achieved, add the soy sauce and butter, and stir well. This caramel sauce can be made up to three days in advance, kept in the fridge and reheated just before using.

• step 8

  Just before you are ready to serve the sweet potatoes, reheat the same oil to 180C or until a cube of bread browns in 30 seconds. Fry the potatoes for 1-2 minutes or until golden brown and crispy. Drain and transfer the potatoes to a bowl, add enough caramel sauce to coat the potatoes, then gently mix.

• step 9

  To serve, pile the potatoes in the middle of a dessert plate, put a scoop of ice cream beside it and finish with a sprinkle of black sesame seeds. Serve while still hot.