Pre-heat your oven to 160C Fan/350F/Gas Mark 4, and grease and line three 8" cake tins (that are at least 2" deep)
Make the sponge by mixing the butter and caster sugar in a large bowl, ideally using an electric hand mixer or in the bowl of a stand mixer, until light and fluffy (about 2-3 minutes)
Add the eggs and buttermilk, and mix until fully incorporated
Add the self raising flour and cocoa powder and mix in gently and just until you can't see any flour anymore
Add the red food colouring and mix gently until you get the desired shade
Divide the mixture between the tins, use scales for accuracy if you like
Bake them for 30-35 minutes or until a skewer inserted in the middle comes out clean. Leave them to fully cool either in the tins or remove from the tins and place on cooling racks
To make the buttercream mix the butter on it's own for a few minutes, then add the icing sugar, vanilla extract and milk, and mix until smooth. Use an electric mixer for best results. If the buttercream is too stiff, you can add more milk
If the cakes have domed on top, level them off with a cake leveller or a serrated knife
Put one of the sponges on a decorating turntable and put some of the buttercream in a piping bag to pipe a border of buttercream around the edge of the sponge - this is to stop the jam seeping into the buttercream that you will spread around the sides of the cake
Fill in the centre of the sponge with half of the jam, then add the next sponge on top
Do the same again - pipe a buttercream border and fill the centre with the remaining jam, then add the final sponge
Use a thin layer of buttercream to fully crumb coat the cake, then put it in the fridge for 30 minutes to firm up
Remove from the fridge and smooth on a final thicker layer of the buttercream, use a palette knife or buttercream smoother to make it smooth all over. Refrigerate again for 30 mins
To make the white chocolate ganache, put the ingredients into a bowl and microwave for 20 seconds, then stir. Continue microwaving in 10 second blasts, stirring between each blast, until melted and smooth
Then add the red food colouring and mix until you have the desired shade
Put the ganache into a piping bag and snip a small section off the end, or put it in a squeezy bottle
Pipe blobs around the edge of the cake, allowing the ganache to drip down the sides in varying amounts
Pipe more ganache on top of the cake and use a palette knife to smooth it out
Then put the remaining buttercream into a piping bag fitted with a nozzle of your choice and pipe rosettes in a circle on top of the cake
Add sprinkles if desired, and a bloody plastic knife for a spooky effect!
Leftovers will keep in an airtight container in a cool place or in the fridge for 3-4 days