In large saucepan, sauté onion in butter until tender. With whisk stir in flour and 1 1/2 teaspoons salt; gradually add milk, stirring constantly, and bring to a boil. Add broth, broccoli and carrots.
Cook over low heat, do not boil, stirring occasionally, about 25 minutes or until carrots are tender. Add pepper and salt, to taste.Servings: Makes 2 quarts