Bring a large saucepan of water to the boil and blanch the spinach for 15 seconds. Reserving the water, drain the spinach and mix with half a teaspoon of the salt.
Add the sweet potato noodles to the reserved water in the pan and simmer for 2–3 minutes. Turn off the heat and leave noodles to soak in the hot water for 5 minutes. Drain the water, return noodles to the pan and mix with 1 tablespoon of the soy sauce, 1 tablespoon of the sesame oil and the sugar.
Heat a wok over medium–high heat and, once hot, add the canola oil and smoked tofu and pan-fry for a little until slightly brown on both sides. Push the smoked tofu aside, add shiitake mushroom and dried black fungus and cook, stirring, for 1 minute.
Add onion, leek and carrot and cook, stirring, for 2–3 minutes until the ingredients are cooked. Add garlic and capsicum and stir for another minute, then add the noodles, white pepper and remaining salt, soy sauce and sesame oil, and stir for 2–3 minutes. Sprinkle with sesame seeds, mix everything well and serve.