PREHEAT oven to 325°F. Melt butter in large saucepan on low heat. Blend in flour and salt. Gradually add milk, stirring constantly. Cook and stir until thickened. Add cream cheese, chocolate and vanilla; cook until cream cheese is completely melted and mixture is well blended, stirring frequently. Remove from heat; set aside. Beat egg yolks with electric mixer on high speed until thick and lemon colored. Gradually add sugar, mixing well after each addition. Gently stir into cream cheese mixture; cool slightly.
BEAT egg whites in large bowl with electric mixer on high speed until stiff peaks form; gently stir into cream cheese mixture. Pour into 1-1/2-qt. souffle dish or casserole dish. With tip of spoon, make slight indentation around top of souffle, 1 inch from edge of dish, to form top hat.
BAKE 1 hour. Serve immediately.