Dark chocolate truffle cake

1) Melt the chocolate in a heatproof bowl over a pan of simmering water.
2) Fold one-third of the whipped cream into the melted chocolate.
3) Remove from heat.
4) Mix in the remaining cream and the amaretti biscuits.
5) Pour into a 18cm loose-base round tin. Chill overnight.
6) Serve sliced and dusted with cocoa and orange segments.