Put the cream in a small pan, then bring just to the boil. Put chocolates in separate bowls, then divide the butter between each. Tip half of the cream over each bowl of chocolate. Leave for about 1 min then stir until melted and smooth. Allow to cool.
Divide the shortbread, fruit and orange zest between the bowls, stir, then chill for at least 4 hrs until firm.
Using a teaspoon, scoop out the mixtures and form into small truffles. Sift the icing sugar onto a plate and roll the white chocolate truffles in it. Do the same with the cocoa and the dark chocolate truffles, then chill until needed. Can be made up
to a day ahead.