Creamy Cheese Sauce

Bahan-bahan (2 porsi)

• 2 tablespoons butter
• 2 tablespoons all-purpose flour
• 1 ½ cups milk
• ¼ teaspoon onion powder
• ⅛ teaspoon white pepper (or a pinch)
• 1 ¼ cups shredded sharp cheddar cheese
• ¼ cup shredded Parmesan cheese