01 - Preheat oven to 350°F. Grease a 9x9-inch baking pan and line with parchment paper, ensuring paper overhangs edges for easy removal.
02 - In a medium bowl, whisk together flour, cocoa powder, salt, and baking powder until thoroughly blended. Set aside.
03 - In a large bowl, combine melted butter and granulated sugar. Whisk vigorously until mixture is smooth and glossy, about 2 minutes.
04 - Add eggs one at a time, beating well after each addition until fully incorporated. Stir in vanilla extract.
05 - Add dry ingredients to wet mixture. Using a spatula, gently fold until just combined. Do not overmix; some small streaks of flour are acceptable.
06 - Fold in chocolate chips and chopped walnuts until evenly distributed throughout batter.
07 - Pour batter into prepared pan. Using an offset spatula, spread evenly into corners, creating a smooth surface.
08 - Bake for 28-32 minutes until a toothpick inserted in center emerges with a few moist crumbs. Avoid overbaking for fudgy texture.
09 - Cool completely in pan on wire rack, about 2 hours. Lift brownies using parchment overhang and cut into 16 squares.