1. Freeze beef for 10 minutes; cut across grain into 1/8-inch-thick slices.
2. Cook noodles according to package directions. Drain and rinse with cold water; drain.
3. 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.
4. Arrange 1/2 cup noodles into each of 4 large bowls. Divide raw beef and chile slices evenly among bowls. Ladle about 1 2/3 cups hot soup over each serving (broth will cook beef). Top each serving with 1/4 cup bean sprouts, 1 tablespoon basil, and 1 tablespoon mint. Serve with lime wedges.