It is ok if the meringues get soft after a while. They get a bit chewy, like a marshmallow, but they hold their shape. If you keep the cakes longer in the refrigerator, decorate them with the meringues at the very last moment.
Prepare 4 metal rings, 5 cm high and 18 cm in diameter. Grease the inside and place on a baking tray with a silicone sheet. Divide the batter in the 4 rings.Bake in a ventilated oven at 175 °C for about 25 to 30 minutes. Test the cakes with a needle to make sure the inside is fully baked. Remove from the oven and turn the cakes over. This way the cakes will flatten on top. Leave to cool completely before continuing. Cut the cakes into 8 discs, 1 cm thick. Start with a chocolate disc and add 150 g of the chocolate butter cream. Place another disc of chocolate cake and add a layer of 200 g of the dark
chocolate truffle cream. Place a 3rd disc of chocolate cake and add another layer of the chocolate butter cream. Top with a disc of chocolate cake. In total, there are 7 layers: 4 layers of cake and 3 layers of butter cream. Be sure to stack the cake layers nice and straight, as it makes it easier to decorate the sides. Cool for 30 minutes in the refrigerator before proceeding.
Decorate the sides and the top of the cakes with a thin layer of butter cream. Use the leftover butter cream to decorate the top of the cakes. Alternate to get a bi-coloured finish. Cut pieces of chocolate meringue of unequal sizes and decorate the cakes all around.