Steam the yam and mash it when it is still hot, then add the sugar.
Heat a pan with the oil and fry the lard.
Remove the lard and use the oil to fry the shallots or onions at low heat.
When the onions turn light brown, add the yam paste and stir through, incorporating the lard oil.
Place a cling film onto the yam paste to ensure moisture does not escape from it.