Preheat your oven to 350°F (175°C). Grease an 8x8 baking pan with cooking spray and line it with parchment paper for easy removal.
In a large mixing bowl, mix the melted butter, granulated sugar, and brown sugar until smooth.
Add the eggs and vanilla extract, and mix until fully combined.
Sift in the unsweetened cocoa powder, flour and salt. Stir until the batter is smooth and fully incorporated.
Fold in the chocolate chips (optional).
Pour the brownie batter into the prepared pan, spreading it evenly.
Bake in the preheated oven for 20-25 minutes. Check with a toothpick inserted into the center— it should come out with moist crumbs for fudgy brownies.
Let the brownies cool completely in the pan before frosting.