Heat oven to 190C/170C fan/gas 5. Butter the base and sides of two round cake pans and line the bases with baking parchment.
In a large bowl, beat together sugar, softened unsalted butter, until creamy. Then add eggs one at a time, then vanilla extract, whisky & milk. Mix together the self-raising flour, cocoa powder, baking powder & a pinch of salt if using unsalted butter. Then combine the dry mix into the butter sugar mix.
Divide the mixture between the prepared cake pans. Bake for 20 mins or until a skewer inserted into the centre of the cake comes out clean. Leave to cool in the tin for 10 mins, then turn out onto a wire rack to cool completely.
Frosting
Melt the chips on medium low heat until melty, then turn off heat and add butter.
Mix powder sugar and cocoa in a seperate bowl and then add into the melted chocolate mixture. Then add whisky and stir in well. Then finally add milk, you'll notice at this point a nice sheen to the frosting.