Preheat oven to 350° F. Butter and lightly flour 9x13 inch baking pan. Sift SWANS DOWN Cake Flour, lightly spoon into measuring cup for 2¼ cups. Cream butter and brown sugar in large bowl until creamy. Gradually beat in flour and oats until crumbly. Stir in chocolate chips and walnuts and set 2 cups of mixture aside. Press remaining mixture into bottom of baking pan. Bake for 12 minutes or until slightly firm. In separate bowl blend cream cheese until smooth. Gradually beat in sweetened condensed milk and vanilla extract. Pour cream cheese mixture over hot crust. Sprinkle remaining flour mixture on top and bake for 25 to 30 minutes. Cool completely and cut into bars. Refrigerate remaining bars.