Separate eggs; put yolks into small mixer bowl and whites into large mixer bowl.
Beat egg yolks at MEDIUM until creamy.
Beat in flour, milk, chives, salt, onion salt, mustard, Worcestershire, and pepper.
Wash beaters and dry.
Beat egg whites until stiff but not dry at HIGH.
Carefully pour yolk mixture over whites; mix at LOW just until blended.
Spoon into well-buttered shallow 2-quart (2 liter) casserole or souffle dish.
Bake in preheated 350°F (180°C) oven for 30 to 35 minutes, or until golden brown.