Cheesy Broccoli Casserole

Bahan-bahan (8 porsi)

• 2 pounds broccoli florets (cut into bite sized pieces, approx. 10 cups)
• 3 tablespoons salted butter
• ½ medium onion (finely diced)
• 3 tablespoons all-purpose flour
• 1 teaspoon dry mustard powder
• ¼ teaspoon salt
• 1 ½ cups milk
• 4 ounces cream cheese (softened, cut into cubes)
• 1 cup shredded sharp cheddar cheese
• ½ cup shredded Parmesan cheese
• 1 cup coarsely crushed buttery crackers (such as Ritz)
• ¼ cup shredded sharp cheddar cheese
• 2 tablespoons salted butter (melted)