Cut the chicken in dices, sprinkle some flour on them and fry them, slowly, until ghey are cooked through but not golden.

Heat the milk with the butter. Once is warm add the cornstarch and the salt and stir. Do NOT let it boil or go near boiling point. When the sauce has a bechamel-like texture add the cheese and keep stiring until melted.

Pour the sauce over the chicken and eat when it's still hot!