Heat oven to 180ºC Grease 20 cm square baking pan. In medium bowl blend butter, sugar and vanilla. Add eggs; using spoon, beat well. Combine flour, cocoa, baking powder and salt; gradually add to egg mixture, beating until welll blended. Spread into prepared pan. Bake 40 to 45 minutes or until brownies begin to pull away from the side of the pan. Cool completely; cut into squares. (16 brownies) Variation Stir one cup of Reese's peanut butter Chips or Hershey's Semi sweet chocolate chips into batter.