Freeze beef for 10 minutes; cut across grain into 1/8-inch-thick slices.
Cook noodles according to package directions. Drain and rinse with cold water; drain.
Place onion and next 5 ingredients (through star anise) in a large saucepan; cook over medium-high heat 5 minutes, stirring frequently.
Add broth and 2 cups water; bring to a boil.
Strain broth mixture though a fine sieve over a bowl; discard solids.
Return broth to pan. Add soy sauce, sugar, and fish sauce; bring to a boil.
Add bok choy and snow peas; simmer 4 minutes or until peas are crisp-tender and bok choy wilts.
Arrange 1/2 cup noodles into each of 4 large bowls.
Divide raw beef and chile slices evenly among bowls.
Ladle about 1 cup of broth into each bowl.
Garnish with bean sprouts, basil, and mint. Serve immediately with lime wedges.