For the sponge:
250 g unsalted butter, plus extra for greasing
150 g quality dark chocolate (70%)
2 tablespoons olive oil
300 g caster sugar
6 large free-range eggs
150 g self-raising flour
4 tablespoons quality cocoa powder
For the chocolate rice layer:
300 g quality dark chocolate (70%), plus extra to serve
1 large knob of butter
1 splash of double cream
100 g puffed rice cereal
For the nougat frosting:
2 large free-range egg whites
3 tablespoons runny honey
200 g caster sugar
½ teaspoon cream of tartar
½ teaspoon vanilla extract
½ teaspoon orange blossom , or rose water, or natural pink food colouring (all optional)