Heat the milk and golden caster sugar in a pan to simmering point.
Melt the butter in a heavy-based pan, add the rice and stir well to coat the grains. Add a ladleful of the hot milk to the rice and stir well. When the rice has absorbed the milk, add another ladleful. Continue to add milk in stages and stir until it is all absorbed. The rice should be slightly al dente, with a creamy sauce.
Add the hazelnuts, sultanas and chocolate and mix quickly. Serve decorated with a little grated chocolate. Don't overmix the chocolate as a marbled effect looks good. For a special treat, add a splash of brandy just before decorating and serving the risotto.