Pre-heat your oven to 160C Fan/180C/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 mixing bowl, ideally with an electric mixer
Add the eggs and milk, and whisk until fully incorporated
Add the self raising flour, cocoa powder and baking powder and whisk in gently until you can't see any flour anymore
Divide the mixture between the tins, use scales for accuracy if you like
Bake them for 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 tin and place on cooling racks
To make the chocolate buttercream mix the butter, cocoa powder and icing sugar together. Once it starts to come together add the milk and mix until smooth. For best results use an electric mixer
To make the M&M buttercream mix the butter and icing sugar together. Once it starts to come together add the milk and M&M Crispy Pieces spread and mix until smooth. For best results use an electric mixer
If the cakes have domed on top, level them off with a cake leveller or a knife
Put one of the sponges on a decorating turntable and pipe a border of chocolate buttercream around the edge of the sponge
Fill in the centre of the sponge with some M&M buttercream, then add the next sponge on top
Do the same again - pipe a chocolate buttercream border and fill the centre with M&M buttercream, then add the final sponge on top
Use some chocolate buttercream to fully crumb coat the cake, then put it in the fridge for 30 minutes to firm up
Coat the cake with a second and thicker layer of chocolate buttercream and smooth it out as best you can using a buttercream scraper tool. Then put it back in the fridge for 30 minutes to set
To make the dark chocolate ganache chocolate drip, 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
OR To make the cheat's dark chocolate drip, melt the dark chocolate in the microwave for 30 seconds, then stir. Continue microwaving in 10 second blasts, stirring between each blast, until melted and smooth. Stir in the vegetable oil
Put your chosen chocolate drip mixture into a piping bag and snip a small section off the end. Or you apply it using a squeezy bottle or a spoon
Pipe blobs around the edge of the cake, allowing the chocolate to drip down the sides in varying amounts
Once the drips are complete you can cover the whole top of the cake with the chocolate drip if you like. Use a palette knife to smooth it out. Put the cake in the fridge for 30 minutes for the ganache to set
Put the remaining M&M buttercream into a piping bag with your chosen nozzle and pipe swirls all around the edge of the cake, spread a little in the centre too for the M&Ms to stick to
Fill the centre with the chocolate M&Ms
Move the cake onto a serving plate or cake stand, and dig in! Leftovers will keep in an airtight container in a cool place for 2-3 days