Step 1: Preheat the oven to 180°C (fan 160°C, gas mark 4). Grease and line three 8” circular cake tins.
Step 2: Cream together the butter and sugar until light and fluffy.
Step 3: Gradually add the eggs one by one, mixing in between.
Step 4: Sift in the flour and baking powder and fold in.
Step 5: In a separate small bowl mix together the cocoa powder and boiling water to a paste then add to the mixture, stirring to combine.
Step 6: Once fully combined, carefully pour into the 3 prepared tins in equal measures.
Step 7: Bake the sponges in the oven for 25-30 minutes or until a skewer comes out clean when inserted in the centre of the cake.
Step 8: Once baked, leave the sponges to cool on a wire rack.
Step 9: Once fully cooled, carefully cut out a large circle from the centre of two of the sponges using a pastry cutter, these will become the bottom and middle sponges.
Step 10: Place the bottom base on a cake board or cake stand that you want to present your cake on (it will be difficult to move once filled).
Step 11: Beat together the icing sugar, cocoa powder and butter to make your buttercream (you may need to add a splash of milk to loosen up).
Step 12: Spread a thin layer of buttercream on the bottom layer of your cake (not covering the hole) and place the second layer on top.
Spread a thin layer of buttercream on the… Step 13: Fill the hole in the centre with your chocolate sweets.
Step 14: Spread a thin layer of buttercream on the top of the sponge and place the remaining sponge layer without the hole on top to seal in the sweets.
Step 15: With the remaining buttercream spread generously on the outside of the cake (or pipe if preferred).
Step 16: Decorate with chocolate sprinkles and serve.