1. Prepare noodles according to package directions. Drain and rinse with cold water. Drain. Snip noodles several times with kitchen shears.
2. Combine 2 cups boiling water and mushrooms in a medium bowl; let stand 20 minutes. Drain mushrooms in a sieve over a bowl; discard mushrooms. Combine mushroom soaking liquid, broth, and next 7 ingredients (through salt) in a Dutch oven. Bring to a boil. Cover, reduce heat, and simmer 20 minutes. Add tilapia; cover and simmer 10 minutes. Stir in noodles and tofu; simmer, uncovered, 5 minutes. Ladle 1 cup soup into each of 8 bowls; sprinkle each serving with 1 1/2 teaspoons green onions.