Preheat your oven to 350°F (175°C) and line an 8-inch square baking pan with parchment paper, leaving some overhang for easy removal later.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes.
Mix in the vanilla extract and salt until well combined.
Gradually add the all-purpose flour and cocoa powder, mixing until just combined. If using chocolate chips, fold them in gently.
Press the dough evenly into the prepared baking pan. Use a fork to poke holes in the surface to prevent bubbling.
Bake in the preheated oven for 20-25 minutes, or until the edges are firm and the center is set.
Remove from the oven and let cool in the pan for about 10 minutes before lifting out using the parchment overhang. Allow to cool completely on a wire rack.
Once cooled, cut into squares or rectangles and serve.