Walnut Sponge Vanilla Cake with Chocolate Diamonds

Usually this cake is made into bars, walnut based cake is baked in a sheet pan, cooled and then buttercream is spread on the top followed with a thin layer of melted chocolate.

Once chocolate hardens, cake is then carefully cut with hot knife into small bars.

I wanted a little change and so I used the same recipe to make a round cake out of it.

I ended up using ganache this time which