Prepare two separate bowls (a similar size if you can!) as you will be making the batters separately before marbling them together.

In the bowl for the vanilla batter, beat together the butter and sugars until light and fluffy.

Beat in the eggs one at a time until fully combined and add the vanilla extract. Beat again until smooth.

Sieve the flour and baking powder into the batter. Add the salt and beat in just until combined. Be careful not to overmix.

In the second bowl, beat together the butter and sugars for the chocolate cake until light and fluffy.

Beat in the eggs one at a time until fully combined and add the natural chocolate & hazelnut flavour. Beat again until smooth.

Sieve the flour, cocoa powder and baking powder into your batter. Add the salt and beat in just until combined. Be careful not to overmix.

Using a large spoon, divide the vanilla mix into the 3 cake tins. Lay a spoonful in random places in the cake tins.

If you can avoid lumping too much of the same batter together and make sure you have plenty of gaps for the other batter, it will bring out a more interesting marble pattern.

When you have used all of the vanilla batter up and you have similar amounts in each cake tin, repeat the process with the chocolate batter. Fill in the gaps you left in the cake tins with the chocolate batter until used up.

Using a knife, swirl through the batters to gently create the marbling pattern you’re after. Be careful not to overdo this as you could end up with the batters just fully combining instead of baking in a beautiful swirling pattern.

Bake for 38 – 45 minutes on the middle shelf. The timing depends on how hot your oven runs. The cakes will be baked through when a cocktail stick comes out clean; the top of the cakes spring back when gently pressed on and the cakes are not making a bubbling/crackling sound when you listen to them.

Allow your cakes to cool in the tins for around 15 minutes and then turn out onto a cooling rack to cool completely.

Whilst your cakes are cooling, make your rice krispie treat characters. Prepare a lined traybake tin or a piece of greaseproof paper/baking parchment on your work surface.

Melt a small knob of butter into a pan over a medium heat.

Add the marshmallows (if using regular size, roughly chop them up before adding) and stir until they have all melted. Stir regularly to avoid the marshmallows catching or burning.

When fully melted, add the rice crisp cereal you are using and stir in until combined. Take off the heat and keep stirring.

Tip into your lined tin or onto the piece of greaseproof paper/baking parchment. Oil your hands (with sunflower/vegetable oil) and press the mixture firmly together and leave for a few moments.

When the mixture is cool enough to handle, add more oil to your hands (this prevents the mixture from sticking to your skin) and begin moulding your characters. A simple thick rectangular figure with a nose for SpongeBob. A thick star-shaped figure in a sitting position for Patrick (don’t forget his belly!). Mould as many jellyfish as you would like to include on your cake: just simple ball shapes.

Line a baking tray and sit your characters on it.

Divide the white chocolate into at least two heatproof bowls: more if using more colours for the jellyfish.

Melt your white chocolate either over bain marie (bowl over boiling water) or in the microwave in 10-20 second bursts. Do one bowl at a time.

Mix in the food colouring until you get the right colour. For example, start with yellow in the first bowl of melted white chocolate. In the next one, mix in pink.

Dip the SpongeBob rice krispie figure into the yellow white chocolate. Use a spoon to help cover the figure completely. Be careful not to crush your piece of art! Lift it out and allow any excess white chocolate to drip back into the bowl before placing back onto the lined baking tray.

Make sure you lay your characters on the lined baking tray in the position you want them to be in when you lay them on the cake. This way you won’t have any visible flat edges where the chocolate has set against the surface of the tray.

Repeat this process with your Patrick figure (in the pink coloured white chocolate) and any jellyfish/other characters you are adding.

Place the baking tray with your characters on in the fridge to set completely.

Make the buttercream.

Beat the butter a little to loosen it before adding the icing [confectioners] sugar. Beat until light and fluffy.

Melt the kinder chocolate bars in a bowl in the microwave in 20 second bursts. Add to the buttercream and beat until combined.

If the buttercream is a little stiff, add a tablespoon of water or milk to loosen it a little.

Spread a little buttercream on the cake board/cake stand you are using and place the first of your cooled sponges over the top.

Spread over some more buttercream – just until covered well – and add the second layer. Repeat until you have stacked all of your cake sponges.

Smooth some buttercream over the entire cake in a thin layer, creating a crumb coat.

Place in the fridge to chill.

Your characters should be set enough by now to finish them. Test this by touching one of them in a less visible place and see if any chocolate comes off onto your finger. If it does, allow them to chill for longer.

Before removing from the fridge, make the clothes and features (i.e. jellyfish legs) for your characters using the various fondant icing (make sure to use white for Patrick’s shorts and SpongeBob’s shirt/legs so that you can paint them). Have fun with this!

When your fondant pieces are ready, take your characters from the fridge and gently press the fondant features to the character figures.

Paint the stripes and tie/collar on SpongeBob’s shirt and socks using the blue, black and red food colouring.

Paint Patrick’s shorts with the purple and green food colouring.

Set aside to dry.

Take your cake from the fridge. Separate the remaining buttercream into 3 bowls and add the blue food colouring to each one in varying amounts. Put the most buttercream in the bowl with the lightest blue colouring as you will cover the top of the cake with this shade. You want to aim for 3 different shades of blue for the ombre effect.

Either pipe or spread the three different colours around your cake with the lightest shade of blue on the top and the darkest around the bottom.

Using a palette knife, smooth the buttercream around your cake to achieve that ombre look. Smooth the top of the cake to your preference.

Using the tip of the palette knife, create a ‘movement’ pattern in the top two shades of blue. It is completely up to you what you want to do so have fun with it! My technique for this cake was to press the tip of the palette knife and lift it to the right as I moved around the cake.

Place your finished characters on the top of the cake to finish.