1. Place the broth and broccoli in a large saucepan or Dutch oven over high heat. Cover, bring to a boil and cook until the broccoli is tender, about 5 minutes.
2. Transfer the mixture to a food processor or blender and process until smooth.
3. Return to the pan and place over medium-high heat. Meanwhile, whisk together the milk, flour, onion powder, garlic powder, and mustard in a large bowl until well blended.
4. Stir the mixture into the pureed broccoli and bring to a simmer, stirring constantly.
5. Reduce the heat and continue to simmer and stir gently until the soup thickens, about 2 minutes.
6. Add the cheese and stir until melted. Season with salt and pepper to taste.
7. Serve in individual bowls and top with Parmesan cheese as desired.