Line a 20cm round baking pan or a 9" square baking pan with non stick paper or grease with non stick cooking spray and set aside.
Crush the Oreos and mix with the melted butter. Press into the base and up the sides of the prepared pan and place in the fridge.
Caramel Filling;
Place the condensed milk, brown sugar and butter in a saucepan over a medium heat. Stir and wait for the butter and brown sugar to dissolve.
Bring it nearly to the boil then remove from the heat. Allow it to cool a little and stir in the vanilla extract.
Pour over the Oreo crust and place in the fridge to set for around two hours.
Chocolate Ganache;
Once the caramel is nearly set, prepare your chocolate ganache.
Place the the cream in a saucepan over a low heat and bring just to boiling point. Take off the heat and pour over the dark chocolate. Mix until smooth.
Pour over the caramel filling and spread in an even layer. Place in the fridge for half an hour to an hour before topping with the Rolos and then allow it to set for another hour or two until you can slice it without the ganache running.