Chocolate Chiffon Cake
Stir cocoa and boiling water until smooth; cool 20 minutes. Mix flour, sugar, baking soda and salt in bowl. Make a well and add in order: egg yolks, cocoa mixture and vanilla. Beat with spoon until smooth. Beat egg whites and cream of tartar in large bowl on high speed until stiff peaks form. Gradually pour egg yolk over egg white mixture gently folding with rubber spatula just until blended.