Begin by cooking the noodles until al dente, according to the instructions on the packet. Drain, reserving a little of the cooking liquid, and then rinse in plenty of cold water until they are completely cool (this will prevent them from sticking), then set aside.
Next make the sauce. Add the sesame paste (or tahini) and peanut butter to a small bowl, along with the soy sauce, rice vinegar and 2 tbsp of the reserved noodle-cooking water, and gradually mix this together. Sesame paste is quite solid and can be difficult to dissolve, but stick with it. Use the back of a fork to mash it in with the liquid ingredients to begin with. Once the sesame paste is incorporated, add the rest of the sauce ingredients. You can add more chilli oil if you want more of a kick. Set aside.
Heat the oil in a heavy-based frying pan or wok over a high heat. Add the minced beef (or mixed beef and pork) and let it brown and caramelise for at least 1 minute, without stirring. Then, stir and continue to cook for 5-6 minutes until browned all over. Once the meat is browned, add the Chinese five spice powder and cook for 30 seconds. Pour in the rice wine and deglaze the pan, then add the sweet bean sauce (or hoisin), soy sauce and black pepper. Mix well and turn down the heat to cook for another 2 minutes.
To assemble, add 50ml of the hot chicken stock or water to each bowl. Add half of the sauce to each bowl and combine with the stock/water. Add half the cooked noodles and sliced greens, then top with half the meat mixture, followed by a tbsp each of the peanuts and sui mi ya cai, and half the spring onions and radishes (if using). Mix it all together and enjoy.