Instructions

1. Preheat oven to 325°F. Line a 10" x 15" jelly roll pan* with parchment paper, and lightly grease the paper.
2. Place the chocolate and butter in a microwave-safe bowl. Heat at half-power in 30-second increments until the butter has melted and the chocolate melts when stirred. Stir until smooth, and then set aside to cool slightly.
3. Whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
4. Place the egg whites in a large bowl, and whisk just until they're foamy. Add the sugar and vanilla, and mix until combined. Next, stir in the cooled chocolate mixture. And finally, stir in the flour mixture.
5. Spread the brownie batter evenly in the prepared pan. Sprinkle the chocolate chips over the top.
6. Bake for 25 to 30 minutes, or until the brownies are firm.
7. Cool in the pan on a wire rack. Then lift the brownies out of the pan and onto a cutting board to break or cut into pieces.