Combine milk and tapioca in a heavy saucepan. Cook, stirring constantly, until tapioca is clear.
Beat egg yolks with sugar and salt. Add 1/2 cup hot milk mixture to egg yolks. Return this to remaining hot milk. Heat again to boiling point. Boil 2 minutes, stirring constantly. Remove from heat. Fold in stiffly beaten egg whites and flavoring. Pour into serving dish. Makes about 10 servings.
