Line the same square pan (from the ube sponge) with plastic wrap.
Press the ube and macadamia nut feuilletine into the bottom of the pan, making sure that it is spread evenly. Use the bottom of a spoon to do this.
Pour the ube mousse mixture on top of the feuilletine and refrigerate until set. *I popped mine into the freezer for about 30 minutes.
Spread an even layer of the white chocolate buttercream onto the set mousse gently.
Layer the Buko all around on top of the buttercream. If the buko layer is not dry, you'll end up with a very soggy droopy mess (I learnt this the hard way).
Place the ube sponge over the Buko layer. Cover the top of the cake with more plastic wrap and refrigerate for another 30 minutes to set.
To remove the cake from the cake pan, we flipped the cake onto a chopping board (to remove the bottom plastic wrap) before flipping it onto the slate where we trimmed the sides of the cake.
Spread the ube ganache layer over the top of the cake evenly. As you only wanted to glaze the top of the cake, this means that you have to be extra careful.
Decorate as you wish. I felt that the mirror glaze was enough and didn't want to ruin it. I did top it off with some wild coriander flowers from the garden.