Preheat the oven to 180 C / Gas 4. Grease two (22cm) cake tins and line with baking parchment.
For the cake:
In a bowl, beat together the sugar and butter until light and fluffy then beat in the eggs, one at a time, until pale and creamy. Sift in flour, cocoa powder and baking powder and mix until well incorporated. Divide the mixture between the two prepared cake tins.
Bake in the preheated oven for 15 to 25 minutes until risen, firm and a skewer inserted into the centre comes out clean. Remove from the oven and allow to cool for a few minutes in the tin before transferring to a cooling rack to cool completely.
For the filling:
Once the cakes have cooled completely, melt the cooking chocolate in a double boiler, or in a pan over barely simmering water.
Place the base cake layer onto a serving plate then spread the chocolate on top and place the second cake layer on top.
For the buttercream icing:
Combine the icing ingredients together in a bowl and beat until a thick, spreadable mixture forms. Once you've made the butter icing, decorate the top of your cake with it. Slice, serve and enjoy.
Enjoy, this is for a medium sized cake, for smaller or bigger ones just adjust the ingredients. Have fun making this! I did :)