Put half the sugar and water in a non-stick saucepan. Allow to boil gradually over a low heat. Add the gingko nuts and simmer until the sugar is absorbed into the gingko nuts. (Keep watching the process of cooking to prevent the sugar getting burnt.)
In the meantime, steam the yam slices until soft. Cool slightly, then put in a food processor with the remaining sugar and 3 tablespoons of oil or lard. Process until smooth. Remove the pureed yam.
Heat a non-stick saucepan with the remaining oil and fry the shallots until golden and crispy. Add yam puree. Stir and fry over a gentle low heat until the paste is well mixed and smooth. Dish out and serve in individual small plates and sprinkle with some gingko nuts. Serve immediately.