Once the cakes have completely cooled, whisk together the non-dairy butter and the icing sugar until you have a creamy, spreadable buttercream.
Stick the 7 inch cake to a cake board with a small amount of the buttercream.
Spread the base of one of the 6 inch cakes with buttercream and stack on top of the 7 inch cake.
Spread a layer of buttercream on top before stacking the second 6 inch cake on top of the first.
Add another layer of buttercream before topping the cake with the 5 inch sponge.
Using a serrated knife, carve the cake so that it has a domed top and gets slightly wider towards the base. You can use any off cuts to fill in any gaps making sure the cake is one smooth shape.
Cover the cake in the buttercream until smooth all over.
Coat a clean work surface with a dusting of icing sugar.
Roll out roughly 750 grams of white fondant into a circle large enough to cover the cake.
Drape the white fondant over the cake and let it naturally create ruffles and pleats. Gently press the fondant into the buttercream to ensure it's secure.
Keep roughly 200 grams of the remaining fondant and place it to one side.
Split the remaining 50 grams in half and colour one half pink and the other half black.
Roll out the pink fondant and cut out two circular rosey cheecks and one "u" shaped mouth.
Roll out the black fondant and cut out two oval shaped eyes.
Pinch four small balls from the remaining white fondant. Press these out gently until they are small, flat discs. Secure these to the black eyes using a little of the leftover buttercream.
Attach the eyes to the cake using some leftover buttercream.
Next, attach the rosey cheeks directly below the eyes, followed by the mouth (again using leftover buttercream as glue).
Finally, split the remaining white fondant in two and roll into two sausage like arms. Pinch the tops of each arms so that they are thinner than the ends.
Attach the arms to the body using the last of the buttercream.
Optional: add a spooky cake topper or even a fondant bow to make it extra cute!