1. Heat oven to 350 degrees F. Line a 9-inch square baking pan with foil. Grease foil. Set aside.
2. Combine flour, baking powder and salt in a medium bowl. Beat butter and sugar in large mixer bowl on medium-high speed 5 minutes, until well blended. Add eggs, one at a time, scraping side of bowl with a rubber spatula. Beat in vanilla. At low speed, gradually add flour mixture until combined. Stir in 1/3 cup of the nuts and the chocolate. Spread batter evenly into prepared pan. Sprinkle remaining nuts over top of batter. Bake 45 minutes, until top is golden brown and a toothpick inserted in center comes out clean. Cool on wire rack. Cut into 12 bars. Makes 12 servings.