For the sponge
400g butter, at room temperature
400g Siúcra Caster Sugar
8 large eggs
2 tsp vanilla extract
400g self-raising flour
2 tsp baking powder
4 tbsp milk

For the buttercream
550g Siúcra Icing Sugar
275g unsalted butter, softened
2 tsp vanilla extract
1-2 tsp milk

For the surprise filling
A mixture of various sprinkles and Smarties

To decorate
Various sprinkles

1.    Preheat the oven to 190 ̊C/170 ̊C fan/gas mark 5. Line four 20cm round cake tins with non-stick parchment paper.

2.    To make the sponges, in a bowl, beat together the butter and Siúcra Caster Sugar until light and fluffy.

3.    Add the eggs one at a time, beating well after each addition. Stir in the vanilla.

4.    Sieve in the flour and baking powder. Add the milk and fold together until just combined.

5.    Evenly divide the mixture between the prepared. Bake for 20-25 minutes or until a skewer inserted in the centre comes out clean.

6.    Transfer to a wire rack and allow the sponges to cool completely.

7.    For the buttercream, beat together the butter, Siúcra Icing Sugar and vanilla until smooth. Add some milk until the buttercream is at a spreadable consistency. Set 80g of buttercream aside for piping later.

8.    Once the sponges are cool, use an 8cm round cutter to cut the middle out of 3 of the sponges. Set the uncut sponge aside, as this will be used last.

9.    To assemble the cake, place one sponge onto a cake board or serving plate, using a teaspoon of buttercream on the board to help the cake stick. Spread on some of the buttercream and add the next sponge on top. Repeat this step.

10.    Before adding the uncut sponge on top, pour various sprinkles and smarties into the hole in the centre. Top with the uncut sponge.

11.    Using a palette knife or offset spatula, spread the buttercream over the top and sides of the cake, making sure to fill in any gaps. There will be crumbs in the icing, so place the cake into the fridge for 30 minutes to set.

12.    Once set, spread over more buttercream to cover any crumbs and smooth out the buttercream.

13.    To decorate, use your hands to press the sprinkles over the top and sides of the cake until completely covered.

14.    Spoon the remaining buttercream into a piping bag, fitted with a star nozzle. Pipe swirls of buttercream around the top edge of the cake.

15.    Serve at the table and cut into the cake to wow your guests with the surprise centre.

Top tip: Lay some parchment paper under your cake before adding the sprinkles. You can re-use the sprinkles that fall, or you can easily add them back into the bottle.