Bring broth to a simmer in a pot over medium heat. Cook broccoli in simmering broth for 15 minutes
Meanwhile, in a separate skillet over medium heat, melt margarine. Add onion and sauté for 5 minutes, or to desired tenderness. Stir flour into onion until pasty. Gradually add milk and stir until thick
Add onion mixture to broccoli mixture in the pot and stir well. Stir in cheese until melted; do not boil. Season with white pepper
