Preheat oven to 400 degrees F. Line a 6" bowl with parchment paper; set aside.

In a small microwave safe bowl, add 2 ounces chocolate chips. Microwave for 30 seconds; stir chocolate. Repeat until chocolate is melted and smooth.

In a medium bowl, beat egg white with an electric mixer until soft peaks form. Add 1/3 cup powdered sugar to egg white, and beat until smooth and creamy.

In a medium bowl, whisk together 1/3 cup powdered sugar, cocoa powder, cornstarch, and salt.

Add cocoa powder mixture to egg white mixture in two additions. Beat until just combined after each addition.

Add lukewarm melted chocolate, remaining chocolate chips, and 1/8 cup nuts. Stir to combine. Mixture will become very stiff, and have a dry texture.

Press dough into prepared dish. If needed, spray you hand with a little non-stick cooking spray to make it easier to manipulate the dough. Place remaining nuts around top of dough and gently press into dough.

Bake for 15 minutes. Dough will look a little puffed up and slightly lighter in color when ready.

Remove from oven and leave cookie in dish for 10 minutes. Using parchment paper, lift cookie out of dish and place on cutting board. Using a sharp knife, cut cookie into 8 wedges. Serve if a big glass of milk or a scoop of vanilla ice cream.