Line an 8" square pan
Combine the butter, golden syrup, chocolate and peppermint extract 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 two chocolates (in small microwavable bowls, checking and stirring at 20 second intervals). Pour over the krispie treats and spread with a spoon to cover.
Add any extra decorations as desired before letting chill for at least an hour before slicing and serving.