Cake Project 3 - Chocolate Buttercream Cake for Elder Brother's Birthday

The nutella cream cake I made on 2 occasions previously was supposed to be my third cake project. Somehow that slipped my mind. Hence, cake project 3 is replaced by this chocolate buttercream layer cake I made for my elder brother's birthday last week.

Using the same chocolate sponge recipe, I decided to use swiss meringue chocolate buttercream to replace the nutella cream. Frosting the cake was a lot easier as compared to using nutella cream. The chocolate buttercream is sturdy even at warm room temperature, making it a brilliant choice of frosting for the tropical climate we experience here all year round.  

The magic of the buttercream does not only lie in the stability at room temperature. It is smooth, chocolatey, buttery and creamy in terms of taste and texture. There is absolutely no gritty feel as compared to icing sugar buttercream. I churned out about 840g of chocolate buttercream and it uses merely 220g of sugar (about 1 cup) as compared to as many as 7 cups of icing sugar for some frosting recipes.

This cake project marks an important milestone in my baking journey. For this baking lesson, I feel that I have achieved several goals. It is my first time doing a complete frosting of an entire cake with buttercream and piped decorations using a cake turntable. While there is still room for more improvement, I am rather pleased with the outcome. The making of this chocolate buttercream layer cake reflects the progress and results of my self-learning process which is akin to studying for a exam paper and receiving the exam results.

I observed something while I was beating the egg whites. The timing at which the sugar is added makes a lot of difference to the resulting texture/ appearance. If the sugar is all added right from the start, the resulting whipped egg whites are likely to be clumpy. However, if the sugar is added when the egg whites have reached soft peaks, the resulting beaten whites will be smooth and glossy, achieving the same effect as when cream of tartar is added. I think this is one reason why when cream of tartar is not used, the instruction usually states that the sugar should only be added when the egg whites are at soft peaks.

Chocolate Buttecream Cake ( Chocolate Sponge Cake recipe adapted from 超人气香港蛋糕56款, chocolate buttercream recipe adapted from Chocolate Ephiphany by Francois Payard)

Serving size: 10 to 12 slices

Taste and texture: Cake base is soft, moist and fluffy. Chocolate buttercream is smooth,creamy, buttery and chocolatey.
Equipment and materials:
1) 8 x 3 inch round pan
2) 9 inch round cake board
3) Cake leveller or palette/serrated knife longer than 8 inches
4) Balloon/wire whisk
5) Rubber spatula
6) Handheld beater/Stand beater
7) Baking paper
8) Wire rack
9) Toothpick/wooden skewer
10) Flour sieve
11) Mixing bowls
12) Cake turntable (optional)
13) Piping tip/s
14) Piping bag/s
15) Coupler for piping

Chocolate Sponge Cake (3 layers):
70g egg yolks, room temperature 
50g caster sugar
4 tbs vegetable oil
4 tbs water
80g cake flour
15g cocoa powder
1/2 tsp baking powder
145g egg whites, room temperature
50g caster sugar

Swiss Meringue Chocolate Buttercream: (about 840g)
195g egg whites
220g granulated sugar
385g unsalted butter, softened but still cold
100g cocoa powder (I used Valrhona, it has a very intense chocolate flavour compared to most brands. Add more if desired.)

Making the Chocolate Sponge Cake:
Prepare Oven: Preheat oven to 160 degrees C.

Prepare flour mixture: Whisk sifted flour, sifted cocoa powder and sifted baking powder in a large bowl to combine.

Making the egg yolk batter: Place egg yolks, 50g caster sugar, oil and water in a large bowl. Mix well with a wire whisk untill the mixture is evenly mixed. Add the flour mixture in and whisk to obtain a smooth and thick chocolatey batter.

Beating egg whites: Next, whisk egg whites on low speed. Increase speed slowly to medium-high and beat untill egg whites are at soft peaks. Add 50g of sugar gradually and beat untill egg whites are just stiff and still moist. This is when the beaters are lifted, the egg whites will form peaks that are upright and not drooping slightly. Egg whites will resemble whipped cream.The entire bowl of whites will not drop out when the bowl is overturned. Do not beat until the egg whites are dry and clumpy.

Folding in egg whites: Using a ballon whisk, fold one third of beaten egg whites into egg yolk batter gently to lighten and combine. Fold in the rest of the beaten whites to combine. Final batter should be foamy and uniform in colour with no streaks of egg white present. Folding egg whites gently using a balloon whisk will prevent egg whites from deflating too much.

Baking the sponge cake: Pour batter into a greased and lined 8 x 3 inch round pan and bake at 160 degrees C for 25 -35 minutes. Test doneness using a skewer or toothpick. The highest part of the cake should rise up to 4/5 or nearly the full height of the tin. When the cake is done, the inserted skewer will come out clean. Cake will shrink from edges on cooling. Unmould sponge cake and leave to cool on a wire rack.

Preparing the Swiss Meringue Chocolate Buttercream:
Dissolve sugar in egg whites: Place 195 egg whites and 220g granulated sugar in a heatproof bowl. Sit the heatproof bowl on a saucepan filled with water. The base of the bowl should not be in contact with the water. This is known as a double boiler. Bring the water in the saucepan to a slight simmer. Use a balloon whisk and stir the egg whites and sugar constantly until the sugar has fully dissolved and the mixture is warm to the touch (test by inserting your finger).

Beating egg whites: Remove the heatproof bowl and beat the warm egg white mixture on medium high speed to obtain stiff peaks using an electric beater. At stiff peaks, the beaten egg whites will not budge when bowl is overturned. When the beaters are lifted from the beaten egg whites, the surface of the egg whites should form stiff upright peaks (not drooping peaks). The beaten egg whites should be cool to the touch (room temperature), not warm like when it was removed from the saucepan.

Adding butter and cocoa: Beat in 385g butter into the beaten egg whites in 3 batches, ensuring each batch is incoporated before adding the next. The egg whites will deflate furiously when butter is added. Continue beating until the mixture is creamy and fluffy (Initially when the butter is added, the mixture may become watery. As more butter is added, the buttercream thickens up). Lastly, sift in 100g cocoa powder and continue beating to obtain a smooth chocolate buttercream.

Assembly:
Slicing sponge cake: Slice sponge cake into 3 even layers using cake leveller or long serrated/palette knife. Slice off the part that has domed.

Preparing the layers: Using the removable base of a round tart tin or a round cake board, slide the tart in base or cake board under a sponge layer and carefully transport the sponge layer onto a 9 inch round cake board placed. This is to prevent the sponge layer from breaking.

Dab some buttercream evenly onto the first layer to seal the crumbs. This is know as a crumb coat. Frost the first layer evenly with 200g of buttercream using a palette knife or spatula. Place a second sponge layer carefully over the frosted 1st layer and align it properly with the 1st layer. Repeat the process of crumb coating and frosting for the 2nd sponge layer.

Once the frosting is done for the first two sponge layers, add the 3rd sponge layer and align it well with the first two layers. For the 3rd sponge layer, do the crumb coat on the surface as well as for the sides of the cake. Once the crumb coat is done, add more buttercream to the surface and sides of the cake and smooth the buttercream using the palette knife. There should be leftover buttercream for piping.

Piping Patterns: Fill a piping bag fitted with a star tip (or any other tip you desire) and pipe rosettes or shells as desired.

Notes:
1) Allow chilled cake to soften at room temperature for 10-15 minutes before serving.
2) Keep cake in an air-tight container after slicing to prevent the cake from drying out.
3) Reduce the amount of buttercream frosting to your liking/preference. Personally, I find the buttercream layers to be slightly thick. Any thicker and there would have been an overdose of frosting.
4) According to Sem (a reader) and Wendy, the addition of sugar to the egg whites at the beginning will result in lower volume of whipped whites as compared to when the sugar is added when the egg whites are at soft peaks.
5) According to Wendy, the addition of cream of tartar or something acidic prevents the egg whites from separating due to overbeating.