Skin yam and dice into small pieces. Steam yam cubes over high heat for around 20 minutes until soft.
Transfer yam to a big bowl and add about 50ml of water, then mash yam using the back of a fork.
Heat oil in a frypan over medium heat and fry shallots till brown and crispy. Remove fried shallots and keep for other purposes, leaving the oil in the frypan.
Reduce to low fire, and add mashed yam, sugar and 100ml of water into frypan. Fry until well-mixed and smooth. *Transfer to a blender to blend if you want the consistency to be smoother.
Let yam paste cool for a little while before serving with coconut milk (about 20ml for each serving) and gingko nuts.