Split the vanilla pod and scrape out the seeds and add to a saucepan with the milk. Bring to the boil. Take care not to burn and turn off heat as soon as boiling point is reached.
Whisk egg yolk and sugar until it goes almost white, then turn off the whisk and add the corn flour. Turn the whisk back on medium and slowly add the hot milk to the bowl, whisking continuously.
Pour the mixture back into the saucepan and bring back to the boil and cook for 1 minute to thicken. Turn off, sieve the mixture into a bowl, cling film and cool down completely in the fridge before using.
Heat the oven to 200 degrees Celcius.
Trace 3 identical circles onto baking paper – approximately 20-22 cm diameter. Place baking paper onto flat baking trays.
Whisk egg and sugar until white and fluffy. The key here, is to whisk for a long time to incorporate as much air as possible as there are not raising agents in the mixture.
Sift flour and vanilla sugar into the egg mixture and fold, very carefully, until completely incorporated. Preserve as much air as possible, so fold carefully but thoroughly.
Carefully divide the batter between the three circles and ensure batter fills the circles all the way around, neatly.
Bake in the oven until just golden brown and done – this will depend on your oven, but 5-6 minutes is usually fine.
Remove from and leave to cool completely on a cooling rack. Very carefully remove the baking paper – if it sticks, wet the back of the paper a little bit and it should come off with more ease.
On high speed, whisk all ingredients for the whipping cream until stiff peaks form. The cream needs to be quite firm to hold when decorating the cake – but take care not to over whip.
Divide the cream into two equal portions. Fold one half of the whipped cream together with the cold vanilla patisserie cream until completely incorporated (The other half is used to decorate the final cake).
Place the first layer cake on the plate you wish to serve on. Spread a nice layer of raspberry jam, follow by a 1cm thick layer of the patisserie cream / whipped cream mixture. Add another cake layer and repeat over again and then add the final cake layer on top (You may have a bit of excess custard cream left).
On the top sponge layer, carefully add the whipped cream in a “dome” shape – you will need to use a spatula here to get it quite smooth all over. You’re looking for around 3-4 cm “top” on the cake. Then carefully place the marzipan lid on top and over the edge of the cake, making sure the sides are completely covered and smooth.
Add the marzipan lid.
If you make your own marzipan lid, add the food colouring to the marzipan and roll it out into a round plate which you then put on the cake.
Sift powdered sugar on top.
Use a piping nozzle and any leftover whipped cream to pipe rosettes of cream around the edge to hide the bottom of the marzipan and any folds.
To make a rose: add few drops of food colouring to the marzipan – add icing sugar if it gets too sticky. Roll out a 1 mm thick piece, 2 cm wide and around 10 cm long. Roll it up loosely, nip the bottom together, spread the leaves a bit and voila: A marzipan rose to the top of your cake
This cake greatly improves after a few hours in the fridge so all the flavours are soaked into the cake layers.