Ingredients

• 5 ounces bittersweet chocolate (60-75% cacao), divided
• 2 tablespoon unsweetened cocoa powder (preferably Dutch-process, sifted after measuring if lumpy
• 3 tablespoon cocoa nibs, (see Shopping Tip), optional
• 1/3 cup egg whites (about 3 large), at room temperature
• 1/2 teaspoon cream of tartar
• 1/2 cup sugar, divided (use 1 1/2 teaspoons less if cocoa nibs are omitted)
• 1/2 teaspoon vanilla extract

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Cooking Directions

Step 1

Position racks in upper and lower thirds of oven; preheat to 350°F. Line 2 baking sheets with parchment paper and coat the paper with cooking spray.

Step 2

Coarsely chop 3 ounces of chocolate and place it in a small microwave-safe bowl. (Alternatively, see "No Microwave?" below.) Microwave on Medium for 1 minute. Stir, then continue microwaving on Medium, stirring every 20 seconds, until mostly melted. Stir until the remaining chocolate melts completely.

Step 3

Chop the remaining 2 ounces chocolate into pieces the size of mini chocolate chips. Combine in a small bowl with cocoa and cocoa nibs (if using).

Step 4

Combine egg whites and cream of tartar in a clean medium mixing bowl. Beat with an electric mixer on low for 30 seconds, then at medium speed until soft peaks start to form. Immediately add about 2 tablespoons sugar; beat for 1 minute. Slowly, about a tablespoon at a time, add the remaining sugar, then vanilla, continuing to beat on medium speed until the mixture is smooth, opaque, glossy and thickened, about 2 minutes longer. Scrape down the sides of the bowl, raise the speed to high, and beat for 30 seconds more. Lightly fold in the chocolate-cocoa mixture and the melted chocolate just until evenly incorporated and no streaks remain; do not overmix. Immediately drop the batter by rounded teaspoonfuls about 1 inch apart onto the prepared baking sheets.

Step 5

Bake the cookies, switching the pans back to front and top to bottom halfway through, until just firm when gently pressed on top but still soft inside, 8 to 12 minutes. Transfer the pans to wire racks and let stand for 1 to 2 minutes. Then slide the paper from the pans to a flat surface and let the cookies cool completely, about 15 minutes. Gently lift the cookies from the parchment paper using a wide-bladed spatula.