To make the yam rings: Steam the yam cubes in a steamer for about 30 minutes until soft. When cooked, mash the yams until there is no lumps and then add in the salt, sugar, 5 spice powder and a tablespoon (15ml) of oil. Mix well and then add the wheat starch flour and knead the ingredients together.
Lightly flour hands and flat surface with the wheat starch flour and shape the yam dough into into a circle about 15 cm in diameter and make a hollow ring.
Heat oil for deep frying in a wok until hot. Place yam ring on a flat spatula and lower in hot oil. Lower heat to medium and fry for 4 minutes until golden brown. Remove and drain on paper towel before placing on serving plate. Fill with chicken cashew nut dish or mixed vegetables and serve immediately.
For the filling: Marinate the chicken cubes with salt, sugar, sesame oil, rice wine and cornflour for about 20 minutes.
Heat a little oil in wok and stir fry the onions until translucent. Add the mushrooms and stir fry for a minute then add the chicken. Stir fry until the chicken is cooked then add the carrots, young corn and snow peas and stir fry for 2 minutes.
Add the sauce ingredients: oyster sauce, soya sauce, rice wine, sesame oil, cornflour, salt and sugar. Mix well and lastly add the cashew nuts and stir fry for another minute and dish out.