Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan, or line with parchment paper, leaving an overhang on the sides to easily lift out the brownies later.
Step 2: In a large mixing bowl, combine the melted butter and granulated sugar. Whisk until smooth and well combined.
Step 3: Add the eggs one at a time, whisking well after each addition until fully incorporated. Stir in the vanilla extract.
Step 4: In a separate medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, and salt. This ensures even distribution of dry ingredients.
Step 5: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix, as this can lead to tough brownies. If using, fold in the chocolate chips or chunks.
Step 6: Pour the brownie batter evenly into the prepared baking pan. Spread with a spatula to ensure a smooth, level top.
Step 7: Bake for 30-35 minutes, or until a toothpick inserted into the center comes out with moist crumbs attached (not wet batter). Overbaking will result in dry brownies.
Step 8: Remove from the oven and let the brownies cool completely in the pan on a wire rack before cutting into squares. Cooling is crucial for fudgy brownies that hold their shape.
Step 9: Once cooled, use the parchment paper overhang to lift the entire slab of brownies out of the pan. Cut into 16 squares and serve. Enjoy your delicious fudgy brownies!