Melt margarine in 2-quart saucepan over medium heat. Add onions; cook and stir until tender. Reduce heat to low. Stir in flour, salt, dry mustard and nutmeg; cook and stir until mixture is smooth and bubbly. Gradually stir in broth. Bring to a boil, stirring constantly. Add carrot and spinach. Reduce heat to medium; simmer 10 minutes or until carrot is tender and spinach is thawed, stirring occasionally. In blender container or food processor bowl with metal blade, puree spinach mixture until smooth. Return mixture to saucepan; stir in milk. Cook over low heatuntil thoroughly heated, stirring frequently. 5 (1-cup) servings