First make the malt sponges. Heat oven to 180C/160C fan/gas 4. Grease and line the bases of 2 x 20cm cake tins with baking parchment. Put the butter and sugar in a large bowl and whisk until pale and fluffy. Add the eggs, one at a time, whisking well between each addition. Tip the flour, malt and baking powder into the bowl with 1/4 tsp salt and fold together, then add the yogurt and vanilla, and give everything a final stir. Divide the cake mixture between the 2 tins, level the tops and bake on the middle shelf for 25-30 mins or until a skewer pushed into the centre of the cakes comes out clean. Cool for 10 mins, then remove from the tins, peel off the baking parchment and transfer to a wire rack to cool completely. Wash the tins.
Now make the chocolate sponges. Grease and line the base of the tins as before and boil the kettle. In the same bowl (don’t worry about washing it), cream the butter and sugar as before, adding the eggs, one at a time, and mixing until combined. Sift in the flour, cocoa and baking powder with 1/4 tsp salt. Fold the mixture together, then add the yogurt, melted chocolate and 100ml boiling water. Stir until combined, then divide between the tins. Bake for 25-30 mins, testing with a skewer as before. Cool in the tins for 10 mins, then turn out, remove the baking parchment and cool completely. The sponges can be made up to 2 days before being iced, cooled and wrapped tightly in cling film.
Make the honeycomb. Grease a baking tray with a little butter or oil. Put the sugar and golden syrup in a large pan. Warm over a medium heat and leave to bubble to a liquid caramel, but don’t stir. When you’re happy with the colour (the darker it gets, the more intense the flavour will be), add the bicarbonate of soda and quickly stir into the syrup. Before the bubbles die down, pour the foaming mixture onto the baking tray, then set aside for 30 mins to cool and firm up.
Make the icing. In your largest mixing bowl, beat the butter with half the icing sugar, the malt and vanilla until smooth. Add the remaining icing sugar and the cream cheese, and beat again until well combined – don’t overmix or the icing may become runny.
You’re now ready to assemble. Put one of the sponges on a cake stand or cake board, sticking it down with a small blob of icing. Use 1/4 of the icing to stack the cakes, alternating between the malt and chocolate sponges. Place the final sponge on top, flat-side up. When assembled, use a palette knife to cover the entire cake with a thin layer of the icing, filling any gaps between sponges, but don’t worry about completely covering the sponges at this stage. This is called a crumb coat and ensures that your final layer is crumb-free. Make space in your fridge and chill the cake for 30 mins to firm up the icing.
Once the icing is chilled, use the remaining icing to completely cover the cake. This is easiest if you pile the icing on top of the cake, then use a palette knife to ease it over the edge and down the sides. You can make it as smooth or as rough as you like. Chill for another 30 mins.
Make the drizzle. Meanwhile, put the dark chocolate in a bowl and heat the cream in a small pan until just steaming. Pour the cream over the chocolate and leave to melt for 5-10 mins. Stir to make a glossy ganache, then set aside to firm up a little – you want the ganache to be pourable but not too runny, to make drizzly droplets down the side of the cake.
When the ganache is the correct consistency, remove the cake from the fridge and spoon the ganache over the top edge of the cake, encouraging it to drizzle down the side with your spoon – start at the back of the cake to get the hang of it. Fill in the middle of the top of the cake with chocolate too.
Break the honeycomb into tall shards and stack them on top of the cake. Finish with whole and halved Maltesers, adding a few around the base, along with some honeycomb crumbs. The cake is best served within 2-3 hrs of assembling, but will still taste delicious for up to 3 days. Store leftovers in the fridge and allow to come back to room temperature before serving.