BOIL water in medium saucepan. Add broccoli; bring to boil. Cover; reduce heat to low. Cook for 5 to 7 minutes or until tender; drain. Place half of broccoli and chicken broth in food processor or blender; cover. Process until smooth.
MELT butter in same saucepan over medium heat. Add onion; cook, stirring occasionally, for 1 to 2 minutes or until onion is tender. Stir in flour. Gradually stir in evaporated milk. Cook, stirring constantly, until mixture comes to a boil. Add broccoli mixture and remaining chopped broccoli. Heat through.