Cut your chocolate sponge cake into halves, leaving you with four equal pieces.
Spread your buttercream on the bottom layer of your cake, crumble some of your chosen cracker on top of the buttercream and drizzle some chocolate ganache on top of the biscuit. Finish off with a sprinkle of mini marshmallows, and use a blowtorch to lightly toast the marshmallows until they colour. Repeat this process the next two layers of cake.
On the top layer, spread some chocolate ganache onto the cake until it drips off the edges and down the sides of the cake.
Once the ganache has slightly set, pipe your Italian meringue in any pattern you’d like on top and blow torch the meringue to give it a toasty colour and flavour. To finish, sprinkle some mini marshmallows on the top.