Broccoli Casserole

Bahan-bahan (4 porsi)

• 3 tablespoons unsalted butter (divided)
• ¾ cup Panko breadcrumbs
• ¼ cup freshly grated Parmesan cheese
• 5 cups coarsely chopped broccoli florets ((about 1 1/4 pounds))
• ¼ cup white whole wheat flour
• 1 ¾ cups non-fat milk
• ½ teaspoon garlic powder
• ¼ teaspoon kosher salt
• ¼ teaspoon dry mustard
• ¼ teaspoon freshly ground black pepper
• ⅛ teaspoon cayenne pepper (optional)
• ½ cup freshly grated extra sharp cheddar cheese