To sifted flour, add baking powder, baking soda, and salt. Sift again. Add nuts.
In an sauce pan, melt butter. Mix in sugar. Cool. Stir in the egg and vanilla. Place in a large bowl.
Gradually add the flour mixture to the sugar mixture. Spread in a 9x9x2 pan that has been well greased. Sprinkle the chocolate chips on top. Bake at 350* for 20 to 25 minutes. DO NOT OVER BAKE. Cool in the pan. Cut into 24 bars.