Melt butter in a saucepan over medium heat. Don’t rush; butter wants to melt at its own chill pace.
Whisk in flour to make a smooth paste. This is your roux—no lumps allowed. Keep whisking for about a minute until it smells lightly toasty.
Slowly pour in milk, whisking constantly. You’re aiming for a silky, light texture; think “pourable sunshine,” not curdled horror.
Stir in cream cheese (if using) and garlic powder. Let it melt and mingle with the milk.
Lower heat and add cheddar cheeses a handful at a time, stirring until melted and smooth. Don’t rush this—melting cheese properly is an art, not a sprint.
Season with salt, pepper, paprika, and a dash of hot sauce or mustard if you like a lil’ kick. Taste and adjust—this sauce wears the crown in the room, so tune it.
If you’re adding chicken, fold in the cooked chicken bites once the sauce is glossy and velvety. Heat through for a minute or two.
Serve warm with your favorite dippers. If it sits too long, give it a quick whisk to reclaim the gloss.