First, separate the egg yolk and egg white. Take 7 egg whites and put them in a big bowl to beat later. The butter should be in room temperature so it is easier to beat. Use a ballon whisk to beat the butter. This will create a very smooth batter later.
Beat the butter and the powdered sugar together on high speed for at least 15 minutes. The butter should be pale and very light.
Put in the egg yolk one by one while still mixing the butter with low speed. After the egg yolks are mixed thoroughly, put in the sifted flour, milk powder, cornstarch, and whipped cream powder. You can put the mixer speed to low and put the dry ingredients slowly.
In a separate bowl, beat the egg whites with high speed for 10 minutes at least or until it reaches stiff peak.
Mix the meringue to the butter mixture with a spatula. Fold and mix until the batter is thoroughly incorporated.
Take some batter (around 225 gr and 100 gr) in 2 small bowls to put in chocolate powder, chocolate paste and mocha paste in another. Mix well.
You can use a piping bag for each batter, the vanilla, chocolate, and mocha batter. Pipe in the batter into a 24 cm bundt pan. You can also use a spatula to put in the batter. Create a beautiful pattern layer by layer. Just be creative.
Put the pan in a pre-heated oven of 180°C for 50 minutes. Check with a bamboo stick to see if the cake is thoroughly baked. When there is no sticky batter on the stick, the cake is done. Take the cake out of the pan and put the cake on a cooling rack. Let it cool completely and you can cut the cake to see the beautiful pattern.
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Notes
Use the balloon whisk when mixing the butter until pale and light. This will make the texture of the cake even smoother.
Beat the meringue until hard peak. Your cake will be firm and sturdy.
Mixing the butter mixture and the meringue has to be thoroughly incorporated. This will make the texture of the cake very smooth.
Keep the cake overnight with a cling wrap. It will make it even moister the next day as the oil from the butter has seeped into the whole cake.
Use a bamboo stick to check if the whole cake is thoroughly baked. If there is still some wet batter on the stick, it is not done yet. You need to continue baking.
Some people will just let the pattern mixes naturally to resemble marble pattern. You can use a bamboo stick to swirl the pattern. I prefer to just pile up each color in the same order. I do not swirl the pattern.
If you bake it in low temperature 300°-320°F (150°-160°C), the outer skin will be very soft and results in the no skin marble cake. If you bake it in 340°-360°F (170° - 180°C), it will have a brownish skin as most marble cake does.