Step 1: Preheat your oven to 350°F (175°C). Line an 8×8 inch baking pan with parchment paper, leaving an overhang on two sides for easy removal, and lightly grease the parchment.
Step 2: In a large bowl, combine the granulated sugar, light brown sugar, and eggs. Whisk vigorously for 2-3 minutes until the mixture is light in color, thick, and frothy. This is key for the crackly top on your brownie.
Step 3: In a separate medium-sized, microwave-safe bowl (or a double boiler), melt the unsalted butter. Add the unsweetened Dutch-processed cocoa powder and chocolate chips (if using) to the melted butter. Stir until the chocolate chips are fully melted and the mixture is smooth and glossy.
Step 4: Pour the melted chocolate mixture into the whipped egg and sugar mixture. Stir gently with a rubber spatula until just combined. Be careful not to overmix at this stage; overmixing can lead to cakey brownies instead of fudgy ones.
Step 5: Fold in the all-purpose flour, vanilla extract, and salt until no streaks of flour remain. Again, mix minimally to ensure a tender, fudgy brownie.
Step 6: Pour the brownie batter into your prepared baking pan and spread it evenly with the spatula.
Step 7: Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs, but not wet batter. The edges should be set, but the center should still look slightly gooey. Remember, a slightly underbaked brownie is a fudgy brownie; overbaking will dry them out.
Step 8: Remove the pan from the oven and let the brownies cool completely on a wire rack before lifting them out of the pan using the parchment paper overhang. For the fudgiest results and cleaner cuts, you can even chill them in the refrigerator for at least an hour before slicing. Enjoy your delicious brownie!