PREHEAT oven to 350°F. Line 9-inch square baking pan with foil, with ends of foil extending over sides of pan. Grease foil.
BEAT butter and sugar in large bowl with electric mixer on medium speed until light and fluffy. Blend in eggs and vanilla. Add flour, baking powder and salt; mix well. Stir in chocolate and pecans. Spread into prepared pan.
BAKE 20 to 25 minutes or until toothpick inserted in center comes out clean. Cool in pan. Lift brownies from pan, using foil handles. Cut into 16 squares to serve.