Preheat the oven to 350°F. Lightly grease an 8x8-inch baking pan with baking spray and line it with parchment paper.
In a large microwave-safe bowl, melt the butter in the microwave in 20-second intervals stirring between each one until fully melted, about 2 minutes. Add the sugar and cocoa and whisk vigorously for 30 seconds. Whisk in the eggs, vanilla, and salt.
Add the flour and chocolate chips and mix together with a spatula until just combined. Spread the batter into the prepared pan. (You can sprinkle the top with more chocolate chips, if desired.)
Bake for about 35 to 40 minutes, inserting a toothpick into the center to check doneness, and removing it with several moist crumbs for fudgy brownies or only a few crumbs for cakey brownies. Let the brownies cool completely in the pan before slicing.