In the top of a double boiler* place sweetened condensed milk, coconut milk, white chocolate chips and butter. Stir constantly until chips and butter are melted. Remove from heat. Add lime juice, and rum and stir until combined. Add coconut. Mix well. Pour into 8x8x2 inch pan prepared before hand by buttering pan and placing waxed paper in the bottom. Cool completely. Cut and serve Store in covered container.
For party fun, place in a small candy paper holder and add a maraschino cherry on top. Garnish with small drink umbrella or pirate flag.