To make the filling, place the pistachios, ground almonds, icing sugar and lemon zest into a food processor together and blitz till fine. Add in the vanilla and enough egg white and blitz to a paste. To make the figollini, roll out the sweet pastry into a long rectangle and brush with water. Roll out the pistachio filling to a sausage the same length and place onto the pastry. Roll over the pastry to create a sausage. Cut into 3 pieces, rolling each piece a little thinner. Cut into 1 inch pieces, close the edges and roll into perfect balls. Place onto lined baking sheets and bake at 200`c for approximately 15 minutes. Allow to cool down completely before dipping into the melted chocolate and covering with coloured sprinkles