Heat the bowl with the chocolate in it over a double boiler to melt the chocolate.
In a sauce pan, heat the ingredients marked with a until the mixture thickens, then remove it from the heat and place a moistened tea towel under the saucepan to cool it down until it's at about 30C.
Use a candy thermometer to measure the temperature.
Add the ingredients marked with a to the melted chocolate and mix.
Transfer this onto a tray covered with parchment paper.
Chill in the fridge to set for a while, then shape into round balls.