• 450 g (1 lb) Jerusalem artichokes (sunchokes), peeled and sliced
• 1.5 litres (52 fl oz) full-cream cow’s milk
• 150 ml (5 fl oz) cream
• 250 g (9 oz) fine cane sugar
• 8 g (¼ oz) salt

Simmer the Jerusalem artichokes in the milk until softened. Add the cream, sugar and salt and heat to 58°C (136°F). Purée the mixture and then leave to cool in the fridge. Transfer to an ice-cream machine and churn until frozen.

If you don’t have an ice-cream machine, pour into a shallow freezer container. Freeze until semi-frozen, then whisk very thoroughly. Freeze and whisk again, twice more.