Put the prawns in a food processor and blitz to a smooth paste. Combine the prawn paste, pork mince, soy sauce, 1 tsp of the sesame oil, the cornflour, egg, garlic, white parts of the spring onion, 1/2 tsp sugar and a pinch of salt together in a bowl.

Spoon about 1 tsp of the filling into the centre of each wonton wrapper. Working with one wrapper at a time, dampen the edge using a little water and fold it in half over the filling to enclose and form a half-moon shape, then dampen one corner and bring it around to meet the other corner and pinch to seal. Repeat with the rest of the wonton wrappers and filling.

Bring 1 litre of water to the boil. Carefully lower in the filled wontons in batches and cook for about 3 mins per batch, or until cooked through. Lift out the cooked wontons into a bowl using a slotted spoon, setting them aside while you cook the rest.

Bring the stock to the boil, then reduce the heat and simmer for 5 mins. Add the remaining sesame oil and stir well. Divide the wontons between bowls, then pour over the broth. Add the green parts of the spring onions and pak choi, if using.