Slice the beef into thin strips.
Mix soy sauce, sesame oil, sherry, and cornflour in a bowl.
Coat the beef in the marinade and rest for several minutes.
Heat oil in a wok until extremely hot.
Stir-fry the beef and marinade for one minute.
Strain the beef through a sieve and discard the liquid.
Wipe the wok clean and reheat with fresh oil.
Stir-fry the onion, garlic, ginger, and chilli for two minutes.
Add red pepper and half the sherry, cooking for two minutes.
Toss in the mangetout and stir-fry for one minute.
Stir in the noodles, pesto, sugar, and remaining sherry until heated.
Add spring onions and drizzle with sesame oil.
Return the beef to the wok and stir-fry for one minute.
Season with pepper and serve garnished with coriander.