Preheat oven to 350 F. Line an 8-inch square baking pan with parchment, leaving a slight overhang on all sides.
Add butter and chocolate to a microwave-safe bowl, and microwave for 30 seconds.
Stir, and continue microwaving and stirring in 15 second intervals until butter and chocolate are melted and smooth. It usually takes me 1 minute total.
Whisk in sugars until well-combined. Batter will look grainy.
Whisk in vanilla and eggs, 1 at a time, until combined. Batter should look smooth and be well-combined.
Whisk in cocoa and salt.
Fold in flour until combined. Batter should be thick.
Pour batter into prepared pan.
Bake for 30-40 minutes, or until toothpick inserted in the center comes out with fudgy crumbs.
Let cool to room temperature in pan.
Cover brownies, and chill for at least 3 hours.
Cut into squares to serve.
Notes
*Good-quality bittersweet chocolate chips will work in place of chopped chocolate.**Be sure to avoid packing the flour. I fluff the flour, scoop, and level. ***Nutrition values are estimates.