Soak noodles in a pot of boiling water covered for 7-10 minutes, after turning off the heat (they must be cooked but al dente). Drain.
In a bowl mix together soy sauce, sugar, five-spice powder and cornflour to form a smooth paste. Add a teaspoon or two of water if the mixture is too thick or lumpy.
Heat the sesame oil in a wok or large pan and quickly fry the ginger and garlic taking care to not burn them. Toss in the vegetables and stir fry on high heat till lightly caramelised and cooked but still crunchy (about 3-4 minutes).
Now add the shrimp, mussels and tomato purée and cook (stirring all the while) till the seafood is done (about 7 minutes). Time to put in the noodles and the soy sauce mixture. Make sure the sauce coats everything as it thickens. Sprinkle sesame seeds on top and serve immediately.