Place your cake on whatever you will be serving it on - once you get decorating it will be difficult to move! I tend to use a plain white dinner plate, which can be moved into the fridge/onto a cake stand as needed.
If you’re making a two layer sandwich cake then start by liberally spreading some buttercream on the bottom layer, and placing the second cake layer on top.
Crumb coat the top and sides of the cake using a spatula. (A crumb coat is an initial thin layer of icing which seals the cake and stops crumbs getting on the final icing layer.)
Then do a second layer of icing, spreading around the sides and thickly on top. The great thing about this cake is that the icing doesn’t have to be neat, so you can leave a bit of texture.
As you ice the sides, allow the icing to spread around the base of the cake on to the plate, to give a border of around 2cm. I suggest using a clean finger to neaten this up and push the icing into any gaps between the cake and the plate.
Now it’s time to get decorating. You want a variation of heights, shapes and textures on the cake. Start with the bigger toppings first e.g. some bourbon biscuits and halved chocolate bars. Stagger these so you can see them all.
Next add the smaller elements such as chocolate buttons, drops and gnawbles. Sprinkle over the top, and add some to the icing around the base of the cake. Also stick some to the sides - a cascading effect can work well.
If you have a chocolate lolly on a stick, now is the time to find a spot for that! Push it well into the cake so that it doesn’t topple over.
Finally, break up a couple of bourbon biscuits into a mixture of crumbs and chunks, and sprinkle these over the cake, including around the base.
Put the cake into the fridge for a couple of hours. This helps the icing set and keeps all the toppings secure.