Angel Food Cake

I was inspired to try this after seeing how the contestants on the Great British Baking Show dealt with this technical challenge. Despite more time - and more directions! - it still took me a bit to master this cake. But, ultimately, it's an easy one to learn - and delicious!
4.5 oz (1 cup plus 2 tbsp) cake flour
0.25 tsp salt
12.25 oz (1 3/4 cups) sugar
12 large egg whites
1.5 tsp cream of tartar
1 tsp vanilla extract
Adjust oven rack to lower-middle position and heat oven to 325 degrees.


Whisk flour and salt together in a bowl. 

Process sugar in the food processor until fine and powder, about 1 minute. Reserve half (6.125 oz) of sugar. Add flour mixture to food processor with remaining sugar and process until aerated, about 1 minute. 

Using stand mixer fitted with a whisk, whip the egg whites and cream of tartar on medium-low speed (speed 4) until foamy, about 1 minute. Increase speed to medium high (speed 8-10), slowly add reserved sugar, and whip until soft peaks form, about 6 minutes. Add vanilla and mix until incorporated. 

Sift flour and sugar mixture over egg whites in three additions, folding gently with rubber spatula after each addition until incorporated. Scrape mixture into ungreased 12-cup tube pan. 

Bake until skewer inserted in center comes out clean and cracks in the cake appear dry, 40 to 45 minutes. Rotate cake halfway through baking. 

Let cake cool completely in pan upside down, about 3 hours. Run a thin knife around the edge of the cake to loosen, then gently tap upside down pan on countertop to release. 
Variations:
  • Lemon-Poppyseed Angel Food cake:
    • Add 2 tbsp grated lemon zest and 2 tbsp juice (from 2 lemons) along with vanilla extract. Fold in 1 tbsp poppy seeds along with flour.
  • Chocolate-Almond Angel Food Cake:
    • Replace 1/2 tsp vanilla extract with 1/2 tsp almond extract. Fold in 2 ounces finely grated bittersweet chocolate into batter following flour. 
  • Cafe au Lait Angel Food Cake:
    • Add 1 tbsp instant coffee or espresso powder to food processor along with the flour being added to the sugar. Replace 1/2 tsp vanilla with 1 tbsp coffee liqueur.
Source: Cook's Illustrated Baking Book

Notes:
  • Do not grease the pan! Angel food cake needs to cling to the pan to maintain its height as it bakes. 
  • From the wizards at CI:
    • All purpose flour will mess with the taste of the cake; use cake flour!
    • Processing the granulated sugar keeps it from deflating the egg whites
    • Keep your yolks clear! Even 1/4 tsp of yolks mixed into the whites kept them from fully whipping up.
    • Processing the flour with the sugar aerates it, as does the sifting. 
    • Cool upside down; angel food cake can collapse under its own weight otherwise.
  • My observations:
    • When they say soft peaks, they mean soft peaks! Stiff peaks are harder to fold the flour into; ultimately it takes more effort, more folding, and thus more deflating of the whites. 
    • What to do with all those yolks?! Make ice cream! or fruit curd!