Not shown in video: Steam the yam pieces for 15-20 minutes or until the taro pieces are thoroughly cooked. Drain and set aside and let cool.
Use a masher or a big spoon to mash the yam until they are completely well-mashed.
Heat up a wok and pour in the cooking oil. Add sliced onions and fry until light brown, then remove and discard.
Add in the mashed yam and continue to stir until the oil and taro are blended. Add water if mixture is too thick.
Keep the heat low and continue to stir for 10 minutes until the yam paste becomes gooey and smooth.
Add the sugar and stir for another couple of minutes.
Add the ginkgo nuts and warm milk and mix well.
Dish up and garnish with sesame seeds and some milk. Serve warm.