Chocolate Chiffon Cake with Chocolate Frosting

Preheat the oven to 325 degrees F (165 degrees C).

Sift cake flour, 3/4 cup sugar, cocoa powder, baking powder, salt, and baking soda together in a large bowl.

Whisk together egg yolks, water, oil, and vanilla extract in a large bowl. Make a well in the center of the flour mixture and add the egg mixture. Whisk until smooth, scraping down the sides of the bowl if necessary.

Combine egg whites and cream of tartar together in a bowl and beat with an electric mixer with a whisk attachment until soft peaks form. Gradually add remaining 3/4 cup sugar and beat until well combined. Gently fold egg white mixture into the batter in 3 portions, until just combined.

Pour batter into an ungreased 10-inch, 2-part tube pan and smooth the top.

Bake in the preheated oven until a skewer inserted in the center comes out clean, 55 to 60 minutes.

Meanwhile, place a metal bowl and wire whisk in the freezer for at least 15 minutes.

Remove cake from the oven. Invert pan onto an upside-down mug to cool completely, about 1 hour. Run a knife around the edges of the cooled cake to loosen it from the pan and carefully transfer it to a cutting board. Use a sharp knife to cut the cake in half horizontally.

Combine sugar, cocoa powder, and vanilla extract in the chilled metal bowl and whisk to combine. Add 2 tablespoons cream and stir. Add remaining cream and beat using the chilled whisk until peaks form.

Bring a saucepan of water to a boil. Combine chocolate, butter, and corn syrup in a metal bowl and place over the saucepan of simmering water. Stir until chocolate is melted, about 3 minutes. Remove glaze from heat and let cool slightly.

Place the bottom half of the cake on a cake plate and top evenly with about 1 cup of frosting reserving the rest for decorating. Carefully place top layer over filling. Pour glaze over the cake and use a spatula to coat the sides of the cake with glaze. Fill remaining frosting into a piping bag and decorate cake to your liking.