1Combine tapioca and water in a medium bowl and stir until smooth. Let stand for 3 hours or until water has risen and separated from starch. Do not mix. Discard water. Starch will be very thick. Slowly mix in egg white and cornflour. The mixture will be thick.
2Place the mushrooms and chillies in a large bowl. Pour over enough warm water to cover. Let stand for 30 mins or until mushrooms and chillies are rehydrated and softened.
3In a big bowl, combine prawns, soy sauce, garlic and pepper. Cover and refrigerate for 30 mins.
4Heat the vegetable oil in a deep fryer or saucepan to 180 C. Add marinated prawns to the batter and mix.
5Drop prawns in small batches into the hot oil. Cook for about 1 to 2 mins or until pale golden brown. Remove and drain on paper towels (the prawns will be fried again before serving).
6To prepare sauce, drain mushrooms and chillies. Cut mushrooms into 3 pcs and chillies in half. Heat the vegetable oil in a large frying pan. Cook onion, carrot and chillies, stirring for 2 mins. Add mushrooms and garlic, soy sauce, sugar, vinegar and 1 cup water. Bring to boil, then reduce heat to medium.
7In a small bowl, blend the cornflour with 1 tbsp cold water. Gradually add cornflour mixture to sauce, stirring to avoid lumps. Simmer for about 5 mins or until sauce has thickened. Season to taste.
8Reheat the oil to 180 C. Deep-fry prawns in batches until golden brown.
9Just before serving, toss the prawns through the sauce. Sprinkle with green onions and sesame seeds.
Photo: Bauer/William Meppem