Chewy Chocolate Cookies

INGREDIENTS

• 3/4 cup all-purpose flour
• 3/4 cup whole-wheat pastry flour
• 3 tablespoons unsweetened cocoa powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon salt
• 6 large egg whites
• 3/4 cup granulated sugar
• 1 1/2 cups packed dark brown sugar
• 1 tablespoon vanilla extract
• 3 ounces unsweetened chocolate, chopped and melted

PREPARATION

1. Position rack in the center of the oven; preheat to 350° F. Line a large baking sheet with parchment paper or a silicone baking mat.
2. Whisk all-purpose flour, whole-wheat flour, cocoa powder, baking soda and salt in a medium bowl. Beat egg whites in a large bowl with an electric mixer until foamy, about 1 minute. Beat in granulated sugar in a slow, steady stream. Scrape down the sides, then beat in brown sugar 1 tablespoon at a time. Beat until smooth, about 3 minutes. Beat in vanilla and melted chocolate. Stir in the dry ingredients with a wooden spoon until just incorporated.
3. Drop the batter by tablespoonfuls onto the  prepared baking sheet, 1 1/2 inches apart.
4. Bake the cookies until flat yet springy, with slightly cracked tops, 10 to 12 minutes. 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.