Potato Doughnuts (fritule)

Place potatoes in a saucepan and cover with water. Bring to the boil, then reduce heat to medium and cook for 40 minutes or until just tender. Drain and set aside. When cool enough to handle, peel and discard skins.
Meanwhile, place sultanas and rum in a small saucepan and bring to the boil. Remove from heat and allow sultanas to soak for 20 minutes.
Return the potatoes to the pan and mash with lemon and orange rinds, nutmeg, vanilla seeds and 55 g sugar until smooth. Add eggs, flour, yeast, soaked sultana mixture and water, and stir for 2 minutes or until the mixture forms a smooth, shiny, thick batter; add more water, 1 tbsp at a time, if necessary. Cover and set aside for 1 hour.
Fill a deep-fryer or large saucepan one-third full with oil and heat over medium heat to 180°C (or until a cube of bread turns golden in 10 seconds). Working in batches, drop teaspoonfuls of batter into the oil and fry, turning halfway, for 2 minutes or until golden.
Remove with a slotted spoon and drain on paper towel. Roll in remaining 220 g caster sugar, to serve.