Break the lime jelly into cubes and then dissolve in 400ml boiling water. Pour into a small bowl and when cool place in the fridge to set.
Place the leaf gelatine in a small bowl of cold water and leave to soften.
Put the cornflour into a small saucepan and add a little of the milk and mix until smooth. Stir in the remaining milk, sugar, vanilla extract and cream. Place over a medium heat and bring slowly to the boil, stirring continuously.
Remove the sauce from the heat. Remove the softened gelatine from the water and add to the sauce, stirring until it has dissolved. Add the white chocolate and stir until it has melted.
Pour the mixture into a 600–700ml jelly mould. When cool, place in the fridge to set.
To remove the blancmange, gently loosen the edge from the mould. Then lower the mould into a bowl of very hot water and hold for a few seconds. (Glass and ceramic moulds will need longer than plastic, and metal moulds need very little time.) Lift out and place the serving dish over the mould. Quickly invert and give a couple of gentle shakes until you feel the blancmange coming away.
Break up the lime jelly with a fork and spoon around the bunny blancmange to serve.