Place mushrooms in small heatproof bowl, cover with boiling water; stand 20 mins, drain. Slice mushrooms thinly.
Meanwhile, heat oil in medium wok; stir-fry onion and garlic until onion softens. Add pork; stir-fry until browned and cooked through. Add mushrooms, water chestnuts, cabbage and sauces; stir-fry until cabbage wilts. Cool.
Preheat oven to moderately hot. Lightly oil oven trays.
Spoon filling onto centre of wrappers; brush edges with egg. Roll each wrapper on the diagonal to enclose filling, folding in sides after first complete turn. Place spring rolls on prepared trays, seam-side down; brush all over with remaining egg. Bake, uncovered, in moderately hot oven about 10 mins or until browned lightly and crisp.
Make dipping sauce. Combine ingredients in small bowl.
Serve hot with dipping sauce.
TIP The pork filling can be cooked and the dipping sauce made a day ahead. Store separately, covered, in the refrigerator.