01 - Place butter in a medium saucepan and melt over medium heat.
02 - Whisk flour into melted butter and cook for 1 minute, stirring constantly, to form a smooth roux.
03 - Slowly pour in milk while whisking continuously until smooth. Bring to a gentle simmer and cook for 2-3 minutes until slightly thickened.
04 - Reduce heat to low. Add cheddar and mozzarella cheeses, stirring until completely melted and smooth.
05 - Stir in garlic powder, onion powder, smoked paprika, pepper, and salt until well combined.
06 - Taste and adjust seasoning as needed. Serve warm over crispy fries or as a dipping sauce.