1. Combine almond flour, 2/3 cup sugar, 5 egg whites and all 10 egg yolks. Whip until thick and pale (to a ribbon).
2. Combine remaining 5 egg whites and 2 tablespoons sugar and warm over a hot water bath. Whip to a meringue.
3. Fold meringue into mixture from step 1.
4. Fold sifted cocoa powder into mixture from step 3.
5. Spread into ½ sheet pan that has been sprayed and lined with parchment paper (baking paper).
6. Bake at 425°F for about 6-8 minutes.