Cheesy Broccoli

Bahan-bahan (4 porsi)

• 1 pound broccoli (cut into florets (about 6 cups florets))
• Water
• 2 tablespoons butter
• 2 tablespoons flour
• 1 cup milk (I used 1%)
• 2/3 cup shredded cheddar cheese
• 2 tablespoons grated Parmesan cheese
• 1/4 teaspoon kosher salt (plus additional to taste)
• Pinch ground mustard (optional)
• Pinch cayenne (optional)