Melt butter in a heavy saucepan over low heat; add flour, stirring until smooth. Cook 1 minute, stirring constantly. Gradually add milk; cook over medium heat, stirring constantly, until thickened and bubbly. Remove from heat; stir in salt and turkey.
Beat egg yolks in a small mixing bowl until thick and lemon colored; gradually stir in one-fourth of hot turkey mixture. Combine yolk mixture with remaining hot mixture, stirring constantly.
Beat egg whites (at room temperature) until stiff but not dry; gently fold into turkey mixture. Spoon into a lightly greased 1 1/2- quart soufflé dish. Bake at 325° for 1 hour or until golden brown.
Note: 1 cup finely chopped cooked chicken may be substituted for turkey.