Preheat oven to 165°C (330°F).
Grate potatoes and set aside.
Combine Grace Coconut Milk and water; add to the grated potato and mix well. Add remaining ingredients and mix well except for the margarine, rum and lime juice.
Scrape mixture into a well greased pan and dot with Grace Hello Soft Margarine and bake for about 2 hours.
Remove cake from oven and allow to cool.
Combine lime juice and rum and pour over pudding before serving.