We've arrived at last at one of the most ambitious cakes in patisserie: The Opera Cake, or Gâteau opéra. From Wikipedia:
It is made with layers of almond sponge cake (known as Joconde in French) soaked in coffee syrup, layered with ganache and coffee,...French buttercream, and covered in a chocolate glaze. Its namesake originates from the layers resembling the levels of an opera theatre
This cake is meant to be decadent yet delicate, with umpteen variations on its many layers making it a popular cake that presents nicely when sliced to reveal its layers. The version of the cake in The Book has three cake layers, two butter cream layers, a layer of ganache, and a layer of glaze, for a total of six.
