Line an 8" square pan
Combine the butter, golden syrup, chocolate and fudge in a small saucepan. Heat on a very low heat, stirring constantly.
Once all melted, turn off the heat. Add in the cereal and stir together.
Press into the pan and chill for 30 minutes.
Melt the milk chocolate (in a small microwavable bowl, checking and stirring at 20 second intervals). Pour over the krispie treats and spread with a spoon to cover. Repeat with the white chocolate, swirling this around for a nice effect.
Add sprinkles or other decorations if desired. Let set for about an hour before slicing. Keep in the fridge in between taking pieces out to eat!