Step 1: Preheat the Oven - Start by preheating your oven to 350°F (175°C). This ensures that your brownies will cook evenly and develop that perfect fudgy texture.
Step 2: Prepare the Baking Pan - Line your 9x13-inch baking pan with parchment paper, leaving some overhang on the sides. This will make it easier to lift the brownies out once they’ve cooled.
Step 3: Melt the Chocolate and Butter - In a microwave-safe bowl, combine the chopped bittersweet chocolate and cubed unsalted butter. Microwave in 30-second intervals, stirring in between until the mixture is completely melted and smooth. Set aside to cool slightly.
Step 4: Mix the Dry Ingredients - In a large mixing bowl, whisk together the all-purpose flour, Dutch-processed cocoa powder, salt, baking powder, and optional espresso powder. This will help distribute the leavening agents evenly throughout the batter.
Step 5: Combine the Wet Ingredients - In another bowl, whisk together the granulated sugar, neutral oil, and the melted chocolate-butter mixture until well combined. Then, add the eggs, egg yolks, and vanilla extract, mixing until smooth.
Step 6: Combine Wet and Dry Ingredients - Gently fold the dry ingredients into the wet ingredients using a rubber spatula. Be careful not to overmix; you want to combine them just until there are no visible streaks of flour.
Step 7: Fold in the Chocolate Chips - Add the semi-sweet chocolate chips or chunks to the batter. Gently fold them in, making sure they’re evenly distributed.
Step 8: Bake - Pour the brownie batter into the lined baking pan and spread it out evenly. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs (but not wet batter).
Step 9: Cool and Serve - Once baked, remove the brownies from the oven and allow them to cool in the pan for about 15 minutes. Then, using the parchment overhang, lift them out and place them on a wire rack to cool completely. Once cool, cut into squares and serve.