Place the biscuits into the Thermomix bowl and crush for 8 seconds, Speed 8. Set aside in a separate bowl.
Melt the sweetened condensed milk, butter and Caramilk chocolate in the Thermomix bowl for 4 minutes, 60 degrees, Speed 2.
Add the desiccated 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.
Spread the mixture into an 18cm x 28cm lined rectangular slice tin and press down firmly.
Melt the extra Caramilk chocolate and vegetable oil or coconut oil in a clean and dry Thermomix bowl for 3 minutes, 50 degrees, Speed 2. Spread the melted chocolate evenly over the slice.
Place the slice into the fridge for a minimum of 3 hours.