In a large bowl, mix the pork mince, sliced prawns, spring onion, salt, white pepper, soy sauce, egg white, flour, and sesame oil together until smooth and sticky.
To make the wontons: place a small portion of filling (about ½ to 1 tsp for larger wontons) onto the centre of each wrapper.Use your finger to dampen the edges of the wrapper with water, then fold and seal. Repeat with the remaining filling and wrappers.
Bring a large pot of water to a boil. Gently add the wontons, stirring to prevent sticking. Cook until the wontons float to the top. Add some cold water, and continue cooking until they float again.
Transfer the wontons to a serving plate. Pour the chilli sauce over them, garnish with spring onion, and drizzle additional chilli oil if desired.