Preheat oven to 350 degrees F (180 degrees C).Measure 1 cup sifted flour. Add baking powder, baking soda, and salt. Sift again. Add 1/2 cup chopped nuts. Mix well and set aside.Melt 1/3 cup butter. Add 1 cup firmly packed brown sugar and mix well. If shortening is used, add 1 tablespoon hot water. Cool slightly.Add egg (beaten) and vanilla. Blend well. Add flour mixture, a little at a time, mixing well.Spread in 9 x 9 x 2 inch pan. Sprinkle 1/2 to 1 cup chocolate chips on top. Bake for 20 to 25 minutes.