Toss the steak slices with the cornflour, 1 tsp of black pepper and the salt. Heat the 3tbsp vegetable oil and the sesame oil in a wok until hot, then fry the steak until dark and crisp (you may have to do this in two batches). Don’t stir the steak too much, or it won’t crisp up. Spoon out the steak and place on a paper towel to remove any excess fat.
Cook the vermicelli noodles as per the pack instructions (usually this means placing in just-boiled water for 3 minutes). Drain and rinse in cold water. Put to one side.
Heat the remaining vegetable oil in the wok and add in the onions and peppers. Stir fry for 3-4 minutes until starting to soften. Add in the garlic and ginger and cook for 1 minute, then add in the soy sauce, sherry, oyster sauce and remaining black pepper and stir.
Whilst the oyster sauce and veg are heating through, cook the noodles.
Heat the chiu chow chilli oil in another large pan or wok. Add the noodles and spring onions and heat through whilst moving the noodles around the pan with a spatula. Mix the soy sauce, lime juice and sugar and pour over the noodles. Allow to heat through, giving the occasional stir to stop the noodles sticking to the pan.
Add the steak back to the wok with the peppers and onions and heat through.
Distribute the noodles between four plates, then top with a lime wedge, chopped chillies, and a sprinkle of sesame seeds. Serve with the steak and vegetables.