Prepare your workspace and tools. Preheat your oven to 350°F (175°C) and line an 8×8 inch baking pan with parchment paper, leaving some overhang for easy removal later.
Melt the butter in a microwave-safe bowl or in a small saucepan over low heat until completely liquid but not hot.
Combine butter and sugar thoroughly. While the butter is still warm, add the granulated sugar and whisk vigorously for about 1 minute until well combined. This helps create that coveted crackly top.
Add the eggs and vanilla to the butter-sugar mixture and whisk until completely incorporated and slightly lighter in color, about 30-45 seconds.
Introduce the cocoa powder by sifting it into the wet ingredients to avoid lumps, then whisk until the mixture is smooth and glossy.
Add the dry ingredients (flour, salt, and baking powder) to the bowl and gently fold with a spatula just until no dry streaks remain. Overmixing will make your brownies tough.
Fold in chocolate chips if using, distributing them evenly throughout the batter.
Transfer the batter to your prepared pan and spread it evenly into the corners using a spatula.
Bake for 25-30 minutes until a toothpick inserted in the center comes out with a few moist crumbs (not wet batter). For fudgier brownies, aim for the shorter baking time.
Cool completely in the pan on a wire rack before lifting out using the parchment paper overhang and cutting into squares.