1. Heat oven to 350°F. Grease 13x9x2-inch baking pan.
2. Stir together flour, cocoa, baking powder and salt. With spoon or wire whisk stir together melted butter, sugar and vanilla in large bowl. Add eggs, stir until well blended. Stir in flour mixture, blending well. Stir in chocolate pieces. Spread batter in prepared pan.
3. Bake 30 to 35 minutes or until brownies begin to pull away from sides of pan. Cool completely in pan on wire rack. Cut into bars. Makes about 24 brownies.