you make a double boiler of out 2 pots. how? place a heavy pot on the stove and fill it with about an inch of water. heat the water over low heat (don't let this boil!). find a smaller pot that will fit into the bigger pot but not touch the water. into the smaller pot place the chips and the condensed milk. stir until the milk and chips and melted and combined.
as soon as the chocolate is melted add in the vanilla and nuts and stir it up quickly. this will set up fast, so you don't have a lot of time. place the mixture into your pan and 