Keep in a double boiler/bain marie to melt ⅔ of the chocolate, white and black chocolate together, melt and add the rest to temper the chocolate (see instructions in post) or if you don't care to temper just melt the chocolate simply.
Once molten, just mix a bit but not fully! We want that marbled effect when pouring the chocolates into the molds.
Pour the chocolate until full into the molds.
Let it cool until hard, this might take a while so keep aside.
Take the chocolates carefully out and store them in a cool place