In a large saucepan, add the milk and 3 ounces of the dark and white chocolates. Turn onto medium heat and stir constantly. When the chocolate begins to melt, add the remaining chocolate and the sugars, and continue constantly stirring with a wire whisk until the chocolate is completely melted. Pour the hot chocolate into coffee cup and top with marshmallows. Brulee with a blow torch. Top with whip cream and toasted coconut.
Propane gas torches are highly flammable and should be kept away from heat, open flame and prolonged exposure to sunlight. They should be used only in well-ventilated areas. Follow torch manufacturer's instructions for use.