Preheat the oven to 180C. Grease and line two 20cm cake tins. Sift the flour, caster sugar, cocoa powder, baking powder and bicarbonate of soda into the bowl of a stand mixer and whisk for one minute to combine. You could also do this using an electric whisk.
In a separate bowl, beat the eggs then add the milk and groundnut oil. Pour into the dry mixture and whisk for two to three minutes until well combined.
With the whisk running, add the boiling water to your mixture a little at a time until combined. The batter will be extremely runny.
Pour into your prepared cake tins and bake in the centre of the oven for 25 – 35 minutes, or until the tops are firm and a skewer or toothpick inserted into the centre comes out clean. Remove from the oven.
For the whiskey syrup: combine the water and sugar in a small saucepan and bring to the boil. Simmer for a couple of minutes until the sugar has dissolved. Add the whiskey and simmer for one minute more then remove from the heat. Trickle the syrup over the top of each cake while still warm then set aside to cool completely.
Make sure your butter is nice and soft. In a stand mixer or using an electric whisk, beat the butter until pale and fluffy. Sift in the icing sugar and whisk to combine, then add the condensed milk. Continue to beat until light and fluffy, slowly incorporating the whiskey until fully combined.
For the ganache: place the chopped chocolate in a medium heatproof bowl. Heat the cream and sugar until the sugar has dissolved. Bring to the boil and simmer for one minute.
Remove the cream from the heat and allow to stand for one minute – pouring it directly over the chocolate will cause it to split. Once it has rested, pour over the chocolate and stir until smooth and glossy, using a rubber spatula or whisk. Set aside for thirty minutes or until it has cooled to a spreadable consistency.
For the truffles: first of all break the chocolate into squares and place it in the bowl of a food processor. Switch on and grind the chocolate until it looks granular, like sugar. Now place the cream, butter and whiskey in a small saucepan and bring these to simmering point.
With the motor switched on, pour the mixture through the feeder tube of the processor and continue to blend until you have a smooth blended mixture. Now add the yoghurt and blend again for a few seconds.
Transfer the mixture, which will be very liquid at this stage, into a bowl, allow it to get quite cold, then cover it with cling film and refrigerate overnight.
The next day, simply sift the cocoa powder onto a flat plate and add the chocolate strands, then take a heaped half teaspoon of the truffle mixture, roll quickly into a ball and dust each one straightaway all over.
To assemble to cake: place one round of cake on a cake stand. Slather over some whiskey buttercream, top with a second round of cake. Dollop your ganache on top of the cake then use a spatula or palette knife to spread it out on top of the cake. Top with a rose of butter cream and place a whiskey truffle on top of each rose.