Place all of the ingredients into a bowl. Heat in a double boiler while stirring constantly with a spatula, until the mixture reaches 42°C.
Remove from the double boiler and stir with a spatula, letting the white chocolate cool gradually.
Once the white chocolate drops to about 25°C, it will thicken, so you can use a spoon to decorate with lines and dots.
Chill in the refrigerator until hardened. Then pour the dark chocolate into the mold and chill in the refrigerator again until hardened.
Story Behind this Recipe
I wanted to make a marbled chocolate, so I experimented. Because I wasn't used to doing this, I first practiced pouring the chocolate into a flat pan before I poured it into the mold. This way I was able to check the consistency of the chocolate first.
This recipe only makes a small amount. I recommend using a silicone or soft mold since tempering the chocolate correctly is difficult and the chocolate may be difficult to remove from the cake mold.