01 - Preheat oven to 350°F. Line a 9×9-inch baking pan with parchment paper or grease lightly.
02 - Whisk together all-purpose flour, cocoa powder, salt, and baking powder in a medium bowl.
03 - In a large bowl, blend melted butter and granulated sugar by whisking until smooth.
04 - Add eggs one at a time into the butter-sugar mixture, whisking well after each addition, then stir in vanilla extract.
05 - Gently fold the dry ingredients into the wet mixture until just combined, taking care not to overmix.
06 - Fold in the semi-sweet chocolate chips or chopped chocolate evenly.
07 - Pour batter into the prepared pan and smooth the surface.
08 - Bake for 28 to 32 minutes, or until a toothpick inserted near the center comes out with a few moist crumbs.
09 - Allow brownies to cool completely in the pan before cutting into 16 squares.