Heat oven to 350°F. Cook and drain pasta as directed on package.
While pasta is cooking, in 3-quart saucepan, melt butter over low heat. Stir in flour, seasoned salt, mustard, pepper and Worcestershire sauce. Cook over low heat, stirring constantly, until mixture is smooth and bubbly; remove from heat. Stir in milk. Heat to boiling, stirring constantly. Boil and stir 1 minute; remove from heat. Using wire whisk, stir in cheese until melted.
Gently stir pasta into cheese sauce. Spoon into 4 ungreased 8-oz ramekins/gratin dishes or 10-oz custard cups. Place filled cups in shallow baking pan (or cookie sheet with sides).
Bake uncovered 20 to 25 minutes or until bubbly.