Bake the cakes the day before you want to assemble them. Preheat the oven to 180C/350F/gas mark 4. Grease a 23cm/9in square tin and line with baking parchment. Line a muffin tin with fairy cake/small cupcake cases.

Sift together the flour, cornflour, bicarbonate of soda, cocoa powder and salt, set aside. Using an electric mixer, whisk together the butter and sugar until well combined. Whisk in the oil a little at a time, whisking well after each addition. Whisk in the egg yolks, vanilla extract and vinegar, beating until well combined.

With the mixture on a low speed, fold in one third of the flour mixture, followed by half the buttermilk, then another third of flour, the remaining buttermilk then the remaining flour.

Add red gel food colouring a little at a time until you reach the desired shade, bear in mind that the colour will darken a fair bit when the cakes are baked so you don't need to get it as dark as you want it to be.

In a clean bowl, vigorously whisk the egg whites with a balloon whisk until good and frothy but not yet beginning to stiffen then fold them into the cake batter.

Pour about three quarters of the mixture into the square tin then divide the remainder among the cupcake cases, I made five fairy cakes and three cupcakes.

Place the square tin on the lower middle oven shelf and the cupcake tray on the upper middle one. Bake the cupcakes for about 15 minutes, until a skewer inserted into the centre comes out clean; remove the cupcakes from the oven and transfer to a wire rack to cool. The large cake will take about 45 minutes to 1 hour to cook, cover loosely with foil towards the end of baking if the top starts to brown too much.

Place the tin on a wire rack and leave the cake to cool in the tin. Once cooled, store the cake and cupcakes in an airtight container.

Once cooled, add red gel food colouring, along with a teeny bit of black, a little at a time until the gel is a deep, dark blood-red colour. Store in an airtight container.

Place the flour in a saucepan, whisk in the milk a little at a time until it is all combined. Place the pan over a medium-high heat and whisk constantly until it thickens to a very thick pudding-like consistency. Scrape into a bowl, cover with clingfilm directly on the surface and refrigerate until cooled.

Whisk together the butter and sugar with an electric mixer on high speed for at least five minutes until very light and fluffy. Whisk in the vanilla extract and salt then whisk in the milk and flour mixture a spoonful at a time until it is all incorporated. Continue to mix until the buttercream is very smooth and fluffy.

Place the chocolate and cream in a bowl, microwave in short bursts, stirring regularly, until melted and smooth. Add food colouring a little at a time until it reaches a blood red shade. Set aside until cooled and thickened but still pourable.

Knead a bit of black fondant into the red fondant to darken it. Break off a piece (about 125g worth) and roll into a ball. Sprinkle a work surface lightly with icing sugar. Roll out the fondant into a rough rectangle about 5mm thick.

Remove the liner from one of the cakes and place it in the middle of the rectangle, fold the two long ends over the cupcake to make a parcel. Fold in the bottom end and trim off the excess. Use your hands to mould it into a sort of heart shape, don't worry too much about any creases or folds, they look great once the hearts have been painted with piping gel. Trim a bit of the excess fondant off the top and use your fingers to form three arteries. Watch the video I linked to above to get a better idea of the technique, it's easier to watch than attempt to visualise the technique.

Repeat with the remaining cupcakes, you can re-use the fondant trimmings. Once the hearts are formed, use a soft paintbrush to brush them all over with the coloured piping gel, I brushed it on quite thickly so it looks like congealed blood.

Use a blob of buttercream to stick one cake round to a serving plate. Spread over a dollop more then place another cake round on top, upside down so that the top is perfectly flat. Carefully spread a thin layer of buttercream over the whole cake, it is quite soft so be gentle; I found the easiest way to do it was to hold the cake steady by placing two fingers on the top while I iced the sides, then gently spread buttercream over the top. It will be very full of crumbs, this is fine and exactly why crumb coats are important! Just make sure you don't get any crumbs back in the bowl of buttercream.

Repeat these steps to make two more mini cakes then place them all in the freezer for about 15 minutes or so until firm.

Spread another, thick layer of buttercream over each cake, using a dough scraper or pallet knife to get it smooth and even. It should be easier to spread this time as the cakes are firm. Once the cakes are smooth, return them to the freezer for another 15 minutes or so.

Remove the cakes from the freezer and drizzle some of the ganache over one side of each cake (if it has thickened too much you can give it a very short blast in the microwave to melt it a bit). Place a heart on top of each cake and serve.