Grease and line an 18 X 28cm rectangular slice tin with baking paper and set aside.
Place the Clinkers and biscuits into the Thermomix bowl and mix on Speed 4, 3-4 seconds or until small chunks remain. Set aside in a separate bowl.
Add the butter and condensed milk to the Thermomix bowl. Melt for 4 minutes, 50 degrees, Speed 2, or until melted.
Return the Clinkers and biscuit chunks to the Thermomix bowl. Mix on 30 seconds, Reverse, Speed 2, (or until combined).
Place into the slice tray and press the mixture down very firmly. Place into the fridge.
In a clean and dry Thermomix bowl, grate the chocolate on Speed 5, 10 seconds. Melt on 50 degrees, Speed 2, 3-4 minutes, or until melted. Pour melted chocolate over the slice.
Place in the fridge for at least two hours (preferably overnight).
Take the slice out of the fridge and leave for 20 minutes before slicing.