Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.
In a medium saucepan, melt the butter over low heat.
Remove from heat and stir in the sugar until well mixed.
Add the eggs one at a time, mixing well after each addition.
Stir in the vanilla extract.
In another bowl, mix the flour, cocoa powder, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until just combined.
If desired, fold in chocolate chips for extra richness.
Pour the batter into the prepared baking pan, spreading it evenly.
Bake for 25 minutes, or until a toothpick inserted comes out with a few moist crumbs.