Place all the ingredients, except the chocolate drops and the pistachios in a food processor and blend until completely smooth, scrapping down the sides as you go. Transfer into a bowl and place in the freezer for an hour.
Remove and roll into small balls. Put back in the freezer while you melt the chocolate, as they need to be cold to work with.
Line a baking tray with tin foil.
Melt the chocolate over a double boiler until smooth. Holding a fudge ball in your hand, dip into the chocolate half way and then roll in the pistachio nuts and place on the tray. Continue with the rest of the balls until finished.
NOTE: Do not put multiple balls in at one time as they will melt into the chocolate!
Place in the fridge until set, approximately an hour. Eat with caution - very addictive!