Place the cream and milk in a small sauce pan and bring to the boil.
Take the mixture off the heat, add in the chocolate cereal, cover with a lid and set aside for 10 minutes.
Drain the liquid through a fine sieve, pour the mixture back into the pan and once again, bring to a boil.
Take the mixture off the heat, add in the dark chocolate (broken into small pieces) and let it sit for 2-3 minutes before giving it a good stir making sure all the chocolate has melted. Cover with cling film and place in the fridge to set overnight.
Scoop the set truffle mixture into 2 teaspoon-sized mounds and roll into a ball. Roll each truffle in cocoa powder.