For the pastry cream, in a large mixing bowl, whisk together the eggs, sugar, flour, cornflour and vanilla and set aside.
Place the milk in a saucepan and bring to a gentle simmer. Remove the pan from the heat and let cool for 1 minute.
Slowly pour half of the hot milk onto the egg mixture, whisking all the time, then add the rest of the milk and return the mixture to the pan.
Bring the mixture back to the boil and simmer for one minute, whisking continuously, or until smooth and thickened.
Pour the cream into a piping bag, secure the open end and once cool, place the piping bag in the fridge.
In a bowl, mash the raspberries with icing sugar and lemon zest. Set aside.
To assemble, remove the cupcake liners from the cupcakes. Cut each cupcake into three layers.
Put the widest layer on a chopping board and spread a little of the mashed raspberries on the cupcake slice, then pipe a layer of pastry cream on top of the raspberries. Put the second layer on top and repeat the layering process - raspberries first then pastry cream. Put the last layer on top.
Beat the cream with the icing sugar until stiff peaks form - you want the cream quite stiff but be careful not to over whip. Spread a layer of cream over the cakes and make a little dome on the top. Put the cakes in the fridge while you prepare the marzipan.
Cut the marzipan block into two pieces - one weighing about 75g and one weighting about 425g. Knead the larger bit of marzipan with a tiny amount of green food coloring, sprinkling some powdered sugar on to your work surface to prevent the marzipan from sticking to it if necessary.
Roll the marzipan out to about 1/2 cm thick and cut out rounds large enough to cover the whole cake. Drape the marzipan over the cakes and smooth out any wrinkles with your hands. Cut off excess marzipan around the edges.
To make the marzipan roses, add a little pink food colouring to the smaller piece of marzipan and knead together to combine.
Roll out very thinly and using the larger end of a piping nozzle, cut 5 circles from the pink marzipan. Lay the circles together in a line, pressing gently with your fingers to secure them. Use your rolling pin to secure them even further if you think they need them. Using a knife cut the circles in half so you are left with 2 lines of half circles and then, working carefully, roll each line up tightly from one end to form a rose.
Decorate the marzipan covered cakes with the roses and serve immediately or store in the fridge until ready to eat.