Preheat your oven to 350°F (175°C). Line or spray a 13x9-inch baking dish and set it aside.
In a medium microwave-safe bowl, combine the butter and chocolate chips. Heat in 30-second intervals, stirring well after each, until melted and smooth.
Stir in the sugar and brown sugar until fully combined.
Add the eggs and whisk thoroughly. Stir in the vanilla extract.
Gently fold in the flour, cocoa powder, and salt until just combined.
Pour the brownie batter into the prepared pan and spread it evenly.
Bake for 25-30 minutes, or until the center is set. Allow the brownies to cool completely before adding the frosting.