Instructions

• Preheat the oven to 350°F (175°C). Line 2 or 3 baking sheets with parchment paper and set them aside.
• In a medium bowl sift together the all-purpose flour and the unsweetened cocoa powder, then add the baking powder. Whisk in the salt and set the dry mixture aside.
• Place the 20 ounces finely chopped bittersweet chocolate in a microwave-safe bowl. Microwave at 50% power, stopping to stir every 30 seconds, until the chocolate is completely melted and smooth. Let the melted chocolate cool for 10 minutes before using.
• In the bowl of an electric mixer, combine the 10 tablespoons room-temperature unsalted butter and 2¼ cups granulated sugar. Cream on medium speed about 3 minutes, until pale and fluffy.
• With the mixer on medium, add the 6 eggs one at a time, beating well after each addition. Increase the mixer speed to high and beat for 3 minutes more, until the mixture is very light, creamy, and pale in color, scraping down the bowl as needed.
• Reduce the mixer speed to low. Add the cooled melted chocolate and the 1 tablespoon vanilla extract and mix just until combined.
• Using a rubber spatula, fold the dry flour/cocoa/baking powder mixture into the chocolate mixture until just incorporated. Fold in the 2 cups chocolate chips until evenly distributed.
• Using a scoop or spoon, portion the dough into 1½-ounce mounds (or a scant ¼ cup) onto the prepared baking sheets, spacing the mounds about 2 inches apart. If the dough is sticky, dampen your hand slightly before flattening each mound gently.
• Bake the cookies in the preheated oven for 14 to 16 minutes, rotating the baking sheet once halfway through, until the tops are evenly cracked and the cookies are softly set.
• Remove the baking sheets from the oven and let the cookies cool completely on the sheets. Use a metal spatula to transfer cooled cookies to a rack or container. Store in an airtight container at room temperature for up to 5 days.