Luckily however, the Reddit user with the nickname SuperDrew124 has revealed the secret behind these special cakes and it goes like that:
Step 1 - you should bloom the gelatin by placing it in water;
Step 2 - you boil glucose and sugar in water;
Step 3 - you remove the mixture off the hub and add the gelatin;
Step 4 - you add the milk;
Step 5 - you pour on the top of the chocolate and buerre mix in order to remove the bubbles.
The mixture should be used at temperature 35C/95F.
The special marble-looking effect comes from the pouring of different color glazes, mixing them together over the tasty cake.