1. In a large bowl mix the chocolate chips and evaporated milk.
2. Heat the mixture in the microwave for 1 1/2 to 2 minutes at Power 7 or Medium-High, until the chips melt.
3. Stir to mix first, and then mix the crushed wafers, sugar, rum and 1/3 cup walnuts.
4. Keep in the fridge for 30 minutes to cool.
5. Shape into 1-inch balls.
6. Chill to firm.