Preheat oven to 325 degrees F.
Line a 9x13 with foil with a large piece of foil so it overhangs lengthwise (so you can pick up the brownies by the foil edges later). Grease with butter or spray with nonstick cooking spray with flour. Set aside.
Melt butter in a small bowl in the microwave. Add chopped chocolate and set aside for approximately 5 minutes then whisk together until chocolate is melted and smooth.
Meanwhile, whisk all of BOWL ONE ingredients together in a medium bowl. Set aside.
Whisk all of BOWL TWO ingredients in a large bowl. Whisk in melted chocolate/butter mixture until incorporated. Stir in flour mixture with a rubber spatula just until combined. Transfer batter to prepared pan and spread into an even layer.
Bake at 325 degrees F until toothpick inserted in the center comes out with a few moist crumbs attached, 25 to 30 minutes, rotating pan halfway through baking.
Let brownies cool completely in pan on wire rack. Using foil overhang, lift brownies out of pan.