In large saucepan, heat butter until melted.Stir in flour, salt, pepper, and onion powder until smooth.Add in milk and broth.Cook until mixture is thickened.Add broccoli. Cook until broccoli is to your desired softness. Some people like to cook the broccoli ahead of time but I didn't. I just simmered for 10-15 minutes after adding broccoli.Remove from heat.Stir in cheese until melted.