In a small saucepan heat the sugar and the cacao together with the water and let it simmer for about 2 minutes. The mixture becomes lightly thick.
Let could the mixture a little bit. Then add the almonds, rum and vanilla and stir well.
Form as much as possible balls and put them on a plate in a way they don't touch each other. Let them cool in the freezer.
Meanwhile melt the chocolate with the pinch of cinnamon.
When the chocolate is melted well take out the chocolate balls and start to roll one after the other in the chocolate until coated. With a fork let drip the excess chocolate and place on the plate. every two/three balls put some pistachio dust on the top.
Place them again in the fridge and let them cool out well until the chocolate forms a hard shell.