Whisk the cornstarch, salt, garlic powder, onion powder, mustard powder, turmeric, and sugar together in a small bowl.
Add the milk and cream cheese to a small saucepan. Bring to a simmer over medium-low heat, whisking frequently, until the cream cheese has dissolved into the milk.
Whisk the spice blend into the simmering liquid and continue to cook for a minute more until it thickens.
Turn off the heat and gently stir in the shredded cheese, folding it into the liquid until completely melted.