Into a bowl sift together the flour, the baking powder, and the salt. In a large bowl with an electric mixer cream together the butter and the brown sugar and beat the mixture until it is light and fluffy. Add the eggs, 1 at a time, beating well after each addition, and stir in the vanilla. Add the flour mixture, stirring until the batter is blended well, and stir in the chocolate chips and the walnuts. Pour the batter into a buttered and floured baking pan, 1 3 by 9 by 2 inches, smoothing the top, and bake it in the middle of a preheated 350° F. oven for 30 to 35 minutes, or until it pulls away slightly from the sides of the pan and a wooden pick inserted in the center comes out with crumbs adhering to it. Let the blondies cool completely before cutting them into serving pieces. cook 032