In a 10- to 12-inch nonstick frying pan over high heat, bring broth and noodles to a boil; stir gently to separate noodles. Boil until liquid is almost gone, about 4 minutes, then add oil.
Stir often until noodles are lightly browned, about 8 minutes. Add chicken, shrimp, and green onions, and stir until hot.
Spoon into wide bowls. Mix soy sauce and mustard and add to taste.