Preheat your oven to 350°F (175°C) and grease a baking pan.
In a saucepan, melt the butter over medium heat.
Remove from heat and stir in the sugar until combined.
Add the eggs one at a time, stirring well after each addition.
Mix in the vanilla extract thoroughly.
In a separate bowl, whisk together the flour, cocoa powder, and salt.
Gradually fold the dry ingredients into the wet mixture until combined.
Fold in chocolate chips if using.
Pour the batter into the prepared pan and spread evenly.
Bake for 20-25 minutes or until a toothpick comes out with a few moist crumbs.