1) Put the pork in a shallow dish. Mix together soy sauce and sherry and pour over meat, coating well. Leave to marinate, in the refrigerator, for 1 hour. 2) Cut leek into thin strips and slice carrot. 3) Heat oil in large frying pan or wok. Remove meat from marinade with a slotted spoon and add to the pan, reserving the marinade. 4) Fry meat, stirring constantly, until browned. Remove meat and keep warm. 5) Add leek, carrot and ginger to the pan and fry, stirring, for 3-4 minutes. 6) Stir in pork, green pepper, sugar, water and marinade. Simmer for 10 minutes. 7) Stir in peas and heat through. 8) Blend vinegar and cornflour together, add to the pan and cook gently, stirring, until sauce thickens. Season to taste and serve.