Place the pork tenderloin in a bowl. Sprinkle with the Chinese five-spice powder and cornflour. Add the soy sauce, sherry and brown sugar. Mix well and leave to marinate while we prepare the remaining ingredients.
Mix all the sauce ingredients in a small bowl. Set aside near the hob so that we have it ready when needed.
Cook the spaghetti in plenty of salted boiling water for one minute less than the time indicated on the packet. Drain and rinse under cold water to stop the cooking process. Toss with the sesame oil and set aside near the hob.
Prepare all the remaining ingredients and arrange them near the hob so that everything is ready for cooking.
Heat the olive oil or vegetable oil in a wok or large frying pan over high heat. Add the pork and stir-fry for 1–2 minutes, until browned and just cooked through. Transfer to a plate and set aside.
In the same wok or pan, add the ginger, garlic and chilli. Stir-fry until fragrant and lightly golden.
Add the green beans and 60 ml of water. Cook, stirring, until the beans have softened slightly but are not overcooked.
Add the red bell pepper and onion. Continue cooking, stirring, until the vegetables have softened slightly while retaining some of their crunch.
Return the pork to the wok or pan. Add the spaghetti, spring onions and sauce. Toss everything together for about one minute, until the flavours come together and the ingredients are evenly coated in the sauce.
Serve immediately, sprinkled with sesame seeds and extra spring onions.