Dark chocolate & orange cake

Ingredients

1 Seville orange

a little melted butter

, for greasing
100g plain chocolate, broken into pieces
3 eggs

280g caster sugar
240ml sunflower oil

25g cocoa powder
250g plain flour
1½ tsp baking powder

orange candied peel, to decorate
For the chocolate ganache
200g plain chocolate, broken into pieces
225ml double cream