In a hot pan, melt some butter over medium heat. Sprinkle in garlic powder and all-purpose flour, cooking for about a minute until the flour takes on a light brown hue. Remember to keep stirring!
Next, pour in the milk and quickly mix it to create a smooth sauce. Ensure the heat remains medium; otherwise, the sauce may thicken too quickly.
Season your sauce with Cajun spices, salt, and pepper, and stir well to blend all the flavors.
Continue stirring, and as the sauce thickens, add in cream cheese and sharp cheddar cheese.
Allow it to blend on medium heat, stirring consistently to achieve a rich and creamy cheesy sauce.