This is a New Zealand version with mashed or sieved potato. We call them Boston Buns in the South Island and Sally Lunns in the North Island.
1 c mashed potato
3/4 c sugar
1 c sultanas
2 c flour
2 tsp baking powder
1/2 c milk
Place mashed potato in a bowl, add the sugar and mix in until a moist mix.
Add sultanas, then sifted dry ingredients.
Lastly mix in the milk to a firm yet sticky dough.
Form two or more buns.
Place onto a greased or baking paper lined tray.
Bake 180ºC 30 minutes (or 25 as small buns).
Ice, sprinkle with desiccated coconut.
Cut when cool.
Icing
1 c icing sugar
50 g butter softened
1 tsp vanilla essence
water to mix
Mix icing sugar, butter, and vanilla together, add water till a thickish consistency.