Steam yam cubes until soft and cooked. Mash until fine while still hot. Add chilli, mushrooms, carrot, water chestnuts, spring onion and coriander leaves. Blend well. Stir in seasoning ingredients, wheat starch and baking powder. Mix well.
Divide into six equal portions. Dust your hands lightly with wheat starch then take one portion and wrap around a sugar-cane stick. Shape well into a drumstick. (If it is sticky, dust with more wheat starch flour.) Dip drumstick into egg white and coat with combined breadcrumbs and cornflakes.
Deep-fry in hot oil until golden. Drain on absorbent paper then serve with dipping sauce.