Line a 28cm x 18cm slice tray with baking paper making sure you leave paper hanging over the sides to help remove the slice from the tin once set.
Cut the butter into cubes and place into your Thermomix bowl. Break one block of the Caramilk chocolate into pieces and add to your Thermomix bowl along with the sweetened condensed milk. Cook for 3 minutes, 60 degrees, speed 2.
Add the biscuits and mix for 10 seconds, speed 7 to blitz. You will need to push the biscuits down towards the blades with your spatula.
If there are still large chunks of biscuits, blitz for a further 10 seconds, speed 7.
Using a metal spoon, spread slice evenly over the tray and push down to smooth.
Break the remaining block of Caramilk chocolate into pieces and place it into a microwave safe bowl along with the coconut oil and cook for 30 second spurts until it has melted.
Pour the melted milk chocolate over the top of the Caramilk Slice and sprinkle the pieces of the flake (optional) and place in the fridge for 2 hours or until set.
Remove the set slice from the baking tray and cut into small pieces (or large - no judgement here!) and enjoy.