Start heating the broth.
Cut the fish into small pieces. Do the same with the scallions and carrot. Thinly slice the ginger.
Put the fish, salt, pepper, ginger, scallions and carrot into the food processor. Process at the highest setting for about 30 seconds. Pour in the egg white and starch solution through the funnel with the motor running. Continue processing for another minute. The mixture should be a thick paste, not pourable.
When the broth is boiling, drop in the fish paste by teaspoonful. Cook in batches so that the broth remains boiling. Cook the fish balls for about 30 to 45 seconds, depending on how large they are. Stir the broth gently to roll the fish balls while cooking. Again depending on how large your fish balls are, the amount of ingredients given above should yield anywhere from 12 to 15 fish balls.
Scoop out the fish balls. Strain the broth.
To make the fish balls noodle soup, place the cooked egg noodles in bowls. Add a few pieces of the fish balls, the blanched Chinese cabbage, carrot and mushrooms, then pour in hot broth.