In a small bowl whisk together the soy, black bean sauce, mirin and sherry. Set aside.
Heat the wok over a high flame then pour in the oil. When the oil is very hot add the chilli, garlic and red peppers and stir fry for 2 minutes, tossing continuously. Add the leeks and cook for 2 minutes more.
Add the ginger and prawns, and cook for about 3 minutes, tossing, until the prawns have turned to brick pink.
Pour in the soy mixture and bubble for about a minute until the sauce has reduced and thickened a little. Remove the wok from the heat and stir in the lime juice.
Serve immediately with some fragrant thai rice or noodles if preferred.