You want to crush the cookies in a bowl, you do your way, we like to pop them into a plastic bag and bang the little fuckers on the counter. Or the wall. But crushing them with a rolling pin works just fine too.
Once crushed, pour the can of condensed milk over them, add the cocoa powder, powdered sugar, melted chocolate and dark rum. Get in there, use your fingers, feel it and thoroughly mix the whole thing up.
Make the balls, (ahem) truffles now and place in the fridge to harden for 30 minutes.
For the topping, melt the chocolate along with the butter in the microwave for 90 seconds, giving it a stir every 30 seconds. Add in the thick cream and mix well.
Using a toothpick, pop each rum ball into the chocolate and leave to harden in the fridge for another 30 minutes on a parchment sheet lined tray. Eat.