- 1. Position the rack in the center of the oven; preheat to 350F. Line a large baking sheet with parchment paper or a silicone baking mat.
- 2. Whisk the all-purpose flour and the whole-wheat flour with cocoa powder, baking soda and salt in a medium bowl.
- 3. Beat the egg whites in a large bowl with an electric mixer until foamy for about 1 minute.
- 4. Beat in granulated sugar in a slow steady stream. Scrape down the sides then beat in brown sugar 1 tbsp at a time. Beat until smooth about 3 minutes.
- 5. Add the vanilla and melted chocolate and mix well.
- 6. Mix the dry ingredients and the liquid ingredients with a wooden spoon until just incorporated.
- 7. Add tbsp of the mixture to the baking tray 1 1/2 inches apart.
- 8. Bake the cookies until flat yet springy with slightly cracked tops - 10 to 12 minutes.
- 9. Cool on the pan for 5 minutes then transfer to a wire rack to cool completely. Let the pan cool for a few minutes before baking another batch; replace parchment paper if torn or scorched.