Preheat the oven to 180 C / Gas 4. Lightly grease a 15cm, loose-bottomed, deep round tin and line the base with greaseproof paper. Grease over the greaseproof paper.
Reserve 100g of the chocolate orange and chop the rest into chunks. Coat these in flour and set aside.
Combine 225g of the butter, the caster sugar, eggs, self-raising flour, baking powder, zest and orange squash into the bowl of an electric mixer with a paddle attachment. Beat on medium speed for about 2 minutes until light and fluffy.
Fold in the chocolate chunks, and pour the mixture into prepared tin.
Bake for 35-50 minutes, or until well risen and golden. A toothpick inserted into the centre of the cake should come out clean.
Leave the cake to cool in its tin for a few minutes, then turn it out onto a wire rack, peel off the paper and leave to cool completely.
For the frosting: pour boiling water into a jug and set a small bowl containing the remaining 100g of chocolate orange and 20g of butter just over the line of the water. Let melt, stirring occasionally until smooth and glossy, and take it off the heat.
Sift the icing sugar and cocoa powder together into a medium bowl. Add the remaining 100g of butter and, using an electric whisk, beat together until combined and an even texture.
Slowly pour in the milk, whisking constantly until you have a smooth, fluffy frosting. Stir in the melted chocolate and butter mixture.
Carefully cut the cooled cake in half and fill the centre with frosting. replace the top and frost the top and sides.
You can, of course, use two sandwich tins instead of one deep tin, but i find cutting the cake in half produces a more even middle surface to frost.
I made this cake using 2 oz of butter, sugar, flour and i egg with the rind of an orange and juice from half. Then for the topping I used Terry's chocolate orange mixed with double cream to make a gnache. It was divine and so easy. The kids polished it off in just over a day. - 09 Jan 2013
This cake is a beautifully tasting one!! It was very hard not to eat the terrys chocolate orange, but I managed!!
So I decided to use 2 sandwich tins instead of making one big cake, as I feel this is more 'cakish'! My family have loved the cake.
It's a fun recipe to try and not too difficult either!
The only annoying bit I found was the sponges seemed quite greasy when I was taking them out of the tins, but not problem!! - 26 Aug 2012
I tried this cake and it was lovely. Although at times it was a little confusing but I got there in the end. I have one tip to make it more orangey is: instead of using milk use orange juice to really bring the orange flavour through. - 14 Dec 2013