Preheat oven to 180°C.
Cut 2 pieces of baking paper making it circular in shape (22cm diameter) enough to line the bottom of 2 separate cake tins.
In a large mixing bowl, place softened butter and sugar, mixing them with a hand mixer or stand mixer for about 1-2 minutes until you have a light and creamy mixture.
Beat and whisk in the eggs one by one into the bowl, then add vanilla and bananas respectively.
In a glass or separate small bowl, mix together baking soda and hot milk until soft.
Pour the mixture into the large bowl, and stir until combined.
Sift in flour and baking powder, gently folding them with a rubber spatula until it thickens up in a few minutes.
Transfer the mixture into prepared tins.
Smoothly press square blocks of the Caramilk chocolate bar into the batter.
Bake for 45 minutes until the top is golden and springy to the touch. Allow to cool before taking them out.
While the cakes cool down, prepare the Caramilk ganache. Heat the cream to a simmer over low heat in a bain-marie, then transfer into a separate bowl.
While the cream is still hot, add the Caramilk chocolate to melt, gently whisking them over low speed until you achieve a glossy ganache.
Cool in the refrigerator and stir occasionally to thicken for approx. 2 hours to reach the desired consistency.
Once the ganache has cooled down, prepare the Vanilla Buttercream Icing. In a medium bowl, beat the butter with the hand mixer, adding ½ cup icing sugar at a time.
Add in vanilla and milk and continue mixing for another 1-2 minutes until smooth and fluffy.
When the cakes are cool and the ganache is ready, glaze the top of one cake with the ganache and then gently lay the second cake, completely forming one whole cake.
Coat the cake with Vanilla Buttercream Icing as needed.
Decorate the top of the iced cake by glazing the remaining ganache, sprinkling and spreading out the chopped / smaller chunks of the Caramilk bar.
Chill before serving