Preheat your oven to 350°F (175°C) and grease a baking dish.

In a large bowl, combine melted butter and sugar until well mixed.

Add eggs one at a time, mixing well after each addition. Stir in vanilla.

In a separate bowl, sift together flour, cocoa powder, and salt.

Slowly incorporate dry ingredients into the wet mixture until just combined.

Fold in chocolate chips if using.

Pour batter into the prepared baking dish and spread evenly.

Bake in preheated oven for 25-30 minutes or until a toothpick comes out clean.

Let cool before cutting into squares and serving.