Preheat the oven to 350°F (175°C). Grease an 8x8-inch baking pan or line it with parchment paper.
In a mixing bowl, whisk together cocoa powder, sugar, flour, and salt until well combined.
Melt the butter in a saucepan over low heat; let it cool slightly before adding to the dry ingredients.
Add eggs to the cooled butter mixture and whisk until smooth. Combine this mixture with the dry ingredients until just mixed.
Fold in chocolate chips if using. Pour the batter into the prepared pan and bake for 20-25 minutes until a toothpick comes out clean.
Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
For the ganache, heat heavy cream and chocolate chips in a saucepan until melted and smooth; pour over cooled brownies and allow to set before cutting into squares.
