Mix all the ingredients (except for the chocolate) in a food processor, adding a tiny bit of warm water until you get a sticky, very thick paste.
Shape this paste into about 18 small balls.
Melt the chocolate bar in a very small saucepan on very low heat.
Coat each ball with the melted chocolate and place on parchment paper or a grill, and sprinkle with ground pistachios.
Place in the fridge or freezer until the chocolate becomes solid again. I recommend storing these truffles in the freezer before serving, as the flavors will further develop. Enjoy.