Broccoli and Parmesan Casserole

Ingredients

• 8 cups coarsely chopped broccoli florets (about 2 pounds)
• 1/3 cup all-purpose flour (about 1 1/2 ounces)
• 1/4 teaspoon salt
• 1/4 teaspoon dry mustard
• 1 1/2 cups fat-free milk
• 1 cup fat-free less-sodium chicken broth
• 2 tablespoons diced pimientos drained
• 1/4 teaspoon freshly ground black pepper
• Cooking spray
• 12 garlic melba toast rounds