01 - Preheat oven to 350°F. Line a 9x9-inch baking pan with parchment paper or grease it lightly.
02 - Whisk together flour, cocoa powder, salt, and baking powder in a medium bowl.
03 - In a large bowl, blend melted butter and granulated sugar thoroughly using a whisk.
04 - Add eggs one at a time to the butter-sugar mixture, whisking well after each addition, then stir in vanilla extract.
05 - Fold dry ingredient mixture gently into the wet ingredients until just combined; avoid overmixing.
06 - Fold in semi-sweet chocolate chips or chopped chocolate evenly throughout the batter.
07 - Pour batter into the prepared baking pan and smooth the surface with a spatula.
08 - Bake for 28 to 32 minutes until a toothpick inserted near the center emerges with a few moist crumbs.
09 - Allow brownies to cool completely in the pan before cutting into 16 squares.