1. Line an 18cm cake tin with baking paper.

2. In a microwaveable bowl, put the broken-up white chocolate, golden syrup and butter. Carefully melt it in the microwave, 10 seconds at a time, stirring in between. This will take a few minutes but be patient so the mixture doesn't split or go grainy. If you don't have a microwave, do this step in a heatproof bowl over a pan of simmering water, stirring until smooth.

3. Add the vanilla and the green food colouring until the mixture turns a nice deep green. If you don't use enough colouring, your trees won't look like trees!

4. Put the Rice Krispies into a large mixing bowl, then pour in the green chocolate mixture. Mix it well until it's all combined and the cereal has all turned green. We found this easiest to do by hand. If it's not green enough, add a bit more colouring.

5. Pour the mixture into the cake tin and press down until it's smooth and flat on top.

6. Put the tin into the fridge to set for a couple of hours. Don't rush this stage or it'll be difficult to cut!

7. Carefully take it out of the tin and cut it into half, then quarters and eighths. You should end up with 8 Christmas tree shapes.

8. Make the icing by adding a couple of teaspoons of water to the icing sugar, then use it to create 'tinsel'. You can use a piping bag or do it by hand.

9. Decorate with sweets, and then leave to set. Merry Christmas!