Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan, or line it with parchment paper, leaving an overhang on the sides to easily lift the brownies out later. This step ensures your brownies won't stick and makes for easy cleanup.

In a large bowl, melt the unsalted butter. You can do this in the microwave in 30-second increments, stirring in between, or in a small saucepan over low heat on the stovetop.

Once the butter is melted and slightly cooled, add the granulated sugar to the bowl with the butter and whisk until well combined. Then, beat in the large eggs one at a time, followed by the vanilla extract. Make sure each egg is fully incorporated before adding the next.

In a separate medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, and salt. Whisking these dry ingredients together beforehand ensures they are evenly distributed, preventing pockets of flour or cocoa in your finished brownies.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed or by hand until just combined. Be careful not to overmix at this stage; overmixing can lead to tough brownies.

Gently stir in the semi-sweet chocolate chips. Feel free to use milk or dark chocolate chips for a different flavor profile, or even a mix! This addition gives your brownies an extra burst of luscious chocolate goodness.

Pour the batter evenly into the prepared baking pan and spread it out. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs (not wet batter). The exact baking time will depend on your oven.

Once baked, remove the pan from the oven. Let the brownies cool completely in the pan on a wire rack. This is crucial for achieving those perfect, fudgy squares. Once fully cooled, lift them out of the pan using the parchment paper overhang and cut into desired squares.