1.Place noodles in a small heatproof bowl, cover with boiling water, stand until just tender; drain.
2.Heat oil in a wok over high heat; stir-fry mushrooms for 2 minutes or until golden and tender. Add wombok, beans and carrot; stir-fry for 1 minute or until almost tender. Add sprouts, noodles, 2 tablespoons of the char siu sauce, half the tamari and half the sesame seeds; stir-fry for 30 seconds or until heated through. Drain, reserving cooking liquid.
3.Halve bean curd sheets. Top with ½ cup of the vegetable mixture. Fold sheet over filling, then fold in both sides. Continue rolling to enclose filling. Repeat with remaining vegetable mixture and sheets to make a total of eight rolls.
4.Steam rolls, covered, over a large wok of simmering water for 10 minutes or until bean curd is tender.
5.Meanwhile, whisk cornflour and reserved cooking liquid in a small saucepan until combined. Stir in remaining char siu sauce, tamari and seeds. Place pan over medium-high heat; cook, uncovered, for 5 minutes or until mixture boils and thickens.
6.Serve vegetable rolls with sauce; sprinkle with extra sesame seeds, if you like.