Preheat oven to 350°F (180°C). Spray a 13x9-inch baking pan cooking spray. Line pan with parchment paper, letting excess extend over sides of pan.
In the top of a double boiler, place 1⅓ cups (227 grams) chocolate morsels and butter. Cook over simmering water, stirring occasionally, until chocolate is melted and mixture is smooth. Turn off heat, and whisk in sugars. Remove from heat, and let cool slightly.
In a medium bowl, whisk together flour, black cocoa, and salt. Set aside.
In a small bowl, lightly whisk eggs. Add half of beaten eggs to chocolate mixture, whisking until combined. Add remaining beaten eggs, and whisk until combined. Whisk in vanilla. Fold in flour mixture until a few bits of flour remain. Fold in remaining 1 cup (170 grams) chocolate morsels. Spread batter into prepared pan.
Bake until a wooden pick inserted in center comes out with a few crumbs, 35 to 40 minutes. Let cool completely in pan. Using excess parchment as handles, remove from pan, and cut into squares. Store in an airtight container for up to 3 days.
Notes
*We used Guittard Extra Dark Chocolate Baking Chips.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/black-cocoa-brownies/