Cream together the butter and sugar until light and fluffy (approx. five minutes).
Beat in the vanilla.
Slowly start to add in the flour alternating with the condensed milk mixing well between each addition.
Stir in the chocolate chips and walnuts if using.
Shape into one inch balls and placed onto baking sheets lined with parchment paper.
Refrigerate for one to two hours until firm.
Melt the candy coating and one by one dip the truffles into the melted coating, let the excess drip off then place back onto the lined baking sheet.
Chill for a further 15-30 minutes.
Place melted white chocolate or any remaining dark chocolate into a piping bag and pipe lines across each truffle.
Chill for a final 30 minutes then it is finally time to eat!!
Store in the refrigerator.