Heat oven to 180°C
Pierce sweet potatoes, place on a tray and bake 50–60 mins until tender
Cool sweet potatoes completely
Grease 6 dariole moulds
Pour boiling water over dates, add bicarbonate of soda, leave 15 mins, then mash
Peel cooled sweet potatoes
Whisk potato flesh with butter, sugar, eggs, vanilla and the date mixture
Sift in flour, baking powder and salt
Fold to combine
Reduce oven to 160°C
Spoon batter into moulds
Bake 25–30 mins until golden and springy
Melt butter, sugar and date syrup in a saucepan
Once bubbling, remove from heat and whisk in yoghurt and salt
Let sauce thicken slightly as it cools
Turn out puddings while warm
Spoon over sauce, add flakey salt and chopped toasted hazelnuts
