The original recipe makes 24 cookies. I personally enjoy cookies that are one bite, especially those with powdered sugar. My ‘stache and goatee, don’t need to be any whiter than they already are. Therefore, instead of making them golf ball size, I used a #100 ice cream scoop  to form them about half the size of the original recipe.
Also, having learned the hard way on the last batch, it is possible to let the batter sit too long. As it sits, it becomes increasing stiff. This makes it next to impossible to form, especially if using an ice cream scoop. Therefore, don’t let it sit longer than about 15 minutes before forming and rolling in the sugar.
1 cup (about 6 ounces) bittersweet chocolate, finely chopped
3 cups (12 ounces) powdered sugar, divided
1/2 cup (1 1/2 ounces) unsweetened cocoa powder
1 tablespoon (1/4 ounce) cornstarch
1/4 teaspoon salt
3 large egg whites (6 ounces), room temperature
1 pinch cream of tartar
½ cup (about 3 ounces) dark chocolate baking chips
Preheat oven to 400°F. Line 2 large baking sheets with parchment paper.
Melt the finely chopped chocolate in a small heat-proof bowl over simmer water, stirring until just melted. Set aside to cool slightly.
Whisk 1 cup sugar, cocoa, cornstarch, and salt in medium bowl to blend and set aside.
Using a stand mixer with the whisk attachment, beat egg whites until foamy. Add cream of tartar and continue beating to soft peaks.
Gradually beat in 1 cup sugar. Continue beating until mixture resembles soft marshmallow cream.
On low speed, beat dry ingredients into meringue. Stir in lukewarm chocolate and chocolate chips. Wait about 10 minutes to allow dough to become very stiff.
Place the remaining 1 cup sugar in bowl. Roll 1 rounded teaspoon of dough into ball; roll in sugar, coating completely. Place on prepared sheet.
Repeat with remaining dough, spacing 2 inches apart. Bake until puffed and tops crack, about 10 minutes. Cool on sheets on rack 10 minutes. Transfer to rack to cool completely.