Combine the melted butter and granulated sugar and vigorously whisk until combined. Add the eggs and vanilla extract and whisk to combine.
Add the flour, baking powder and salt and fold together until a batter forms. Add in the chocolate and fold until the chocolate is incorporated into the batter.
Pour the batter into an 8x8 inch pan lined with parchment paper and sprinkle with more chocolate if desired. Bake for 38-40 minutes. Let cool in the pan. Enjoy!