16 large egg whites (2 cups) (480 ml)
1/3 cup (30 grams) unsweetened cocoa powder (I like to use Dutch-processed)
1/4 cup (60 ml) boiling water
2 teaspoons pure vanilla extract
1 3/4 cups (350 grams) granulated white sugar
1 cup (100 grams) sifted cake flour
1/4 teaspoon salt
2 teaspoons cream of tartar
Note: Cream of Tartar is tartaric acid and is a fine white crystalline acid salt which is a by-product of the wine-making industry. It is used when whipping egg whites to stabilize them and to prevent over beating and the whites drying out.
Preheat oven to 350 degrees F (177 degrees C) and place rack in center of oven. Have ready a 10 inch (25 cm) two piece angel food cake (tube) pan.
Separate 16 eggs, whites in one bowl and yolks in another. Cover whites with plastic wrap and bring to room temperature (about 30 minutes). Cover yolks and store in refrigerator or freezer for another use. (Sharon Tyler Herbst in The Food Lover's Tiptionary advises "adding 1/8 teaspoon salt or 1 1/2 teaspoons sugar to each 1/4 cup of yolks (4 yolks) and beat to combine. This inhibits gelatin and whether you add salt or sugar depends on how you will be using the yolks later on." They can be frozen for up to three months or else placed in the refrigerator for a few days.)
In a small measuring bowl combine the cocoa powder and boiling water and stir until smooth. Stir in the vanilla extract.
In another bowl whisk together 3/4 cup (150 grams) granulated white sugar, the sifted cake flour, and the salt.
In a large mixing bowl, with the whisk attachment, beat the egg whites until foamy. Add the cream of tartar and continue to beat until soft peaks form. Gradually beat in the remaining 1 cup (200 grams) granulated white sugar until stiff peaks form.
Remove 1 cup (240 ml) of the beaten egg whites and whisk it into the cocoa powder mixture to lighten it.
To the remaining egg whites, gradually sift the flour mixture over the egg whites (about 1/4 cup at a time) and gently but quickly fold the flour into the egg whites, using a large wire whisk or a large rubber spatula. Once you have incorporated the flour mixture into the egg whites fold in the cocoa powder mixture. (It is important not to overmix the batter or it will deflate.)
Pour the batter into the pan (will be almost full, the pan is left ungreased so the batter can cling to the sides of the pan as it bakes and allows it to reach its full volume.) and run a metal spatula or knife through the batter to get rid of any air pockets. Smooth the top and bake in the oven for about 40 - 45 minutes or until a wooden skewer inserted in the center of the cake comes out clean and the cake springs back when gently pressed. The top of the cake will have cracks.
Immediately upon removing from the oven invert the pan so the baked cake will maintain its volume and to keep it from shrinking as it cools. Suspend the pan by placing the inner tube on the top of a soda bottle. Allow the cake to cool for about 1 1/2 hours.
When completely cool, run a metal spatula or knife around the sides of the pan to loosen the cake and then remove the cake from the pan. Next, run a metal spatula or knife along the bottom and center core of the pan and remove. Place onto a serving plate. The cake will keep covered for a few days at room temperature or for about a week in the refrigerator.
This cake can be eaten alone with just a dusting of cocoa powder or confectioners' sugar. Is also wonderful with fresh berries and softly whipped cream.
Serves 12
(joyofbaking.com)