Preheat oven to 180C. Grease and line 4x 20cm cake tins.
Dissolve the instant coffee in 2 tbsp of boiling water, then set aside to cool.
In a stand mixer beat together the butter and sugar until light and fluffy. In a separate bowl measure out the flour and baking powder.
Add the eggs to the butter one at a time, mixing between each one - don’t worry if the mixture looks like it has split, just add a spoonful of the flour mixture.
Next add the flour, cooled coffee and Kahlua and gently fold together, trying to ensure it isn’t overworked.
Spoon the mixture equally into the four cake tins and smooth the top. Bake in the oven for 30 minutes or until a skewer comes out clean. Remove from the oven and place on a wire rack to cool.
Make the syrup: In a saucepan add the instant coffee and 1 tbsp boiling water, then stir to dissolve. Next add the caster sugar and Kahlua to the pan and heat gently. Heat until the sugar has completely dissolved, stirring gently every so often, then remove from the heat and allow it to cool.
Make the ganache: Finely chop the chocolate and place it in a heatproof bowl. Gently heat the cream in a pan until scalding point, but not boiling. Once heated, pour over the chocolate and leave to sit for 3 minutes. Then whisk gently until the ganache is completely smooth. Set aside.
Make the buttercream: Dissolve the instant coffee with 1 ½ tbsp boiling water, and set aside to cool completely. Beat the softened butter in a stand mixer for a few minutes until it is completely smooth. Sieve the icing sugar into a separate bowl. Add the icing sugar bit by bit to the butter until it is combined and smooth. Next add the Kahula and beat again, and finally add the cooled coffee. Beat until smooth.
Assemble: Take each of the cooled cakes and if they are domed, use a serrated knife to level off the top of each cake - they should be equal in height. Brush the syrup over the cut side of each cake, letting it seep in. Place the first sponge cut side down and then using a palette knife smooth over some buttercream, followed by some ganache. Place the second sponge on top and repeat until you have stacked all four sponges. Next use the rest of the buttercream to ice the sides and top of the cake, smoothing as you go. Then place the whole cake in the fridge to allow the buttercream to set.
Place the rest of the ganache in a squeezy bottle - you may need to reheat the ganache over a pan of simmering water if it is too thick, you need it to be drip consistency. Remove the cake from the fridge. Use the bottle to create drips down the sides of the cake working from the top. Finish by covering the top of the cake in ganache and smoothing with a palette knife. Decorate with chocolate coated coffee beans and chocolate shards.