Melt margarine in large nonstick saucepan over medium heat. Add mushrooms, carrot and onion; cook and stir 3 minutes. Add broth, spinach, nutmeg and pepper; mix well.
In small bowl, combine milk and flour until well blended. Add to spinach mixture; cook, stirring constantly, until thickened and bubbly. Reduce heat to low. Add cream cheese and Swiss cheese; cook and stir until melted. Serve immediately.
