For the cherry filling : Keep aside the cherries needed for decoration and chop up the remaining cherries. Reserve about 4 tbsp of the apple juice to dissolve the corn-starch and use the rest to make the filling. Put the pitted cherries and half the apple juice/ liquid in a blender and blend till smooth.
Put this in a pan, with the remaining apple juice/ liquid in which the cherries were preserved, sugar (according to taste and depending on how sweet the cherries are) and the lime juice and bring to a boil. When this has reduced a bit, add the dissolved corn-starch, mixing it well first, and allow the filling to thicken. Take it off the heat, allow it to cool, and use to fill the cake.
For the soaking syrup : Bring the apple juice and sugar to a boil in a small pan and simmer for about 2 minutes. Take it off the heat and let it cool. Use this syrup to moisten the cake.
For the whipped cream : Refrigerate the cream for about 12 to 24 hours till really thick. Pour into a chilled steel bowl, add the sugar and vanilla essence, and beat with an electric mixer till it forms soft peaks. Add the cornsstarch and beat further till the cream forms stiff peaks which hold their shape. This will take between 6 to 10 minutes. Refrigerate till ready to use. Do this about an hour before you are ready to use the whipped cream.
For the cake : Melt the butter and cocoa powder over hot water and mix well. Cool till it is lukewarm but of pouring consistency.
In another bowl beat the egg yolk and sugar, using a electric beater, over hot water till it is pale, creamy and increases in volume. This will take about 2 minutes.
In a third clean and stainless steel bowl, beat the egg whites and salt till they form soft peaks.
Sift the flour and baking powder onto the egg yolks and then pour the chocolate mixture also into this bowl. Do not mix. Add one third of the beaten egg whites to the bowl and stir lightly into the batter. Then add the remaining beaten egg whites to the batter and fold carefully making sure everything is well mixed.
Pour into an 8u201d (20cm) round cake tin with a round of parchment paper at the bottom and well-greased sides. Bake at 180C (350F) for about 35 minutes till the top of the cake springs back when touched. Do not over-bake, or the cake will dry out.
Assembling the cake : After the cake has cooled a bit, remove from the tin and neatly cut it into 3 layers horizontally.
Place the top most layer of the cake on your serving plate, with the cut side facing up. Moisten the layer with a few tsp of syrup. Spread one half of the cherry filling on this layer. The use 1/4 of the whipped cream and spread it over this. Place the middle layer over this.
Moisten this layer with the syrup too, and spread the remaining cherry filling over this layer too. Spread another 1/4 of the whipped cream over this. Now place the bottom most layer on top with the underside facing up. Keep aside some of the whipped cream for decorating and spread the rest of the cream on the top and sides of the cake and smoothen it out.
Now decorate the sides with the chocolate curls or shavings and the top as well if you wish. Decorate with piped cream and cherries. If you live in warmer climates, it would be a good idea to refrigerate the cake till you serve it.