Grease and line the base and sides of an 18cm x 28cm rectangular baking tin with baking paper. Set aside.
Place the biscuits into the Thermomix bowl and crush for 8 seconds, Speed 8. Set aside in a separate bowl.
Place the Caramello chocolate (broken into pieces) and butter into the Thermomix bowl and melt for 3 minutes, 50 degrees, Speed 2.
Add the sweetened condensed milk, coconut and crushed biscuits and mix for 10 seconds, Reverse, Speed 5. Scrape down the sides of the bowl and repeat for a further 5 seconds or until well combined.
Press the mixture into the prepared tin and smooth firmly using the back of a spoon. Place into the refrigerator.
In a clean and dry Thermomix bowl, melt the chocolate and vegetable/coconut oil (optional) for 3 minutes, 50 degrees, Speed 2. Pour the melted chocolate over the slice.
Refrigerate for a minimum of 4 hours before cutting into slices.