Step 1: 1. In a food processor or a zip lock bag with a rolling pin to bash, crush together biscuits and 1 packet clinkers. Pour into a large bowl.
Step 3: 2. Chop 3/4 remaining bag clinkers into rough pieces, stir through biscuit mixture.
Step 5: 3. Melt together butter and condensed milk over a low heat in a saucepan. Pour into biscuit mixture, stir to combine. Press into a slice tin or square cake tin lined with foil or baking paper, ensuring overhang so you can lift it out easily. Place in fridge.
Step 7: 4.Melt chocolate and pour over slice. Crush remaining clinkers and sprinkle over. Let set for at least four hours or overnight for best results.