Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius) and line an 8x8 inch square baking pan with parchment paper, leaving an overhang for easy removal.

In a large mixing bowl, vigorously whisk together the melted butter and granulated sugar until well combined and slightly lightened in color.

Add the eggs one at a time, whisking well after each addition, then stir in the vanilla extract until the mixture is smooth and glossy.

Gently fold in the cocoa powder, all-purpose flour, and salt using a rubber spatula. Mix just until the dry ingredients disappear into the batter to avoid tough brownies.

Fold in the semi-sweet chocolate chips if using, then pour the thick batter into your prepared baking pan, smoothing the top into an even layer.

Bake for 20 to 25 minutes. A toothpick inserted into the center should come out with moist crumbs, not wet batter.

Allow the brownies to cool completely in the pan on a wire rack before lifting them out using the parchment overhang and slicing into squares.