- Preheat an oven to 375*F. Mist 2 baking sheets with cooking spray.
- Breakup the chocolate bars and add into microwaveable bowl, heat up on high to melt the chocolate; stirring once halfway through for just 2 minutes, now let it cool for a while.
- A high speed electronic mixer is needed to beat egg whites to give them soft peak. Add 1 cup brown sugar and continue beating mixture. When it appears in creamy form, add vanilla.
- Combine remaining 1/2 cup of brown sugar, arrowroot flour, cocoa in a separate small bowl, now beat into egg whites with slow speed.
- Make a thick mixture by adding in warm chocolate; stirring gently.
- Onto prepared baking sheets, place rounded tablespoon of batter, bake for 10 minutes. Cool on sheet pans for further 10 minutes before placing them on racks to cool entirely.