Line a plate and a board with baking parchment.
To make the truffles break the white chocolate into a small heatproof bowl and place over a saucepan of barely simmering water to melt. Remove from the water and leave to cool for 10 minutes.
Stir the cake crumbs and jam in the melted chocolate until well mixed.
Add approx. 25 drops of bright red gel food colours and mix to make a vibrant red shade. Cover and chill for about 30 minutes or until firm enough to shape.
Meanwhile, start preparing the decoration. Lightly dust the work surface with icing sugar. Cut off a 190g (6 ½ oz) piece of regal-ice, wrap in cling film and set aside.
Roll out the remaining regal-ice piece thinly, and using a small sharp knife, cut out 16 long, thin, oval shapes to resemble rabbit ears.
Place on a board lined with baking parchment, folding the sides in slightly as you lay them down to create more of an ear shape.
Put the board in a warm, dry place for at least an hour until firm enough to hold their shape - you may need to leave them for several hours if the atmosphere is damp.
Gather up the trimmings and wrap in cling film.
Meanwhile, divide the chilled truffle mixture into 8 equal portions. Form into balls and place on the plate lined with baking parchment. Cover and chill for at least 30 minutes until firm.
Divide the reserved large piece of regal ice into 8 pieces. Working on one portion at a time, flatten or roll into a circle about 8cm (3 ¼ inch) diameter and lay a truffle ball in the centre.
Draw up the edges of the circle to enclose the truffle, pinching the top together to completely cover.
Roll the ball carefully in your hands to smooth it. Place on the board lined with baking parchment whilst you cover the remaining truffle balls.
Use the reserved trimmings of regal ice to make 8 pairs of feet, 24 balls for cheeks and tails, and 16 small balls for eyes.
Secure the feet on the bottom of each truffle using a little water if necessary. Stick the tail on the back in the same way, and then stick the cheeks and eyes on the front. Score the cheeks with a sharp knife to make whiskers.
Put a couple of drops of pink food colour gel on a saucer and using a fine paint brush, brush over the inside of the ears and leave to dry. Paint a small pink dot underneath the cheeks for a mouth.
Using the black food colour gel in the same way, paint on eye and nose detail. Leave aside for a few minutes to dry.
When you are ready to serve the truffles, make 2 small slits in the top of each truffle and insert the ears so that they stand upright.
The rabbits are ready to serve and enjoy!