Add chocolate chips and condensed milk to a medium-sized saucepan, heating over low-medium heat until the chocolate chips are completely melted. Add vanilla and stir.
Pour mixture into a mixing bowl, cover with plastic wrap or a lid and chill in the refrigerator for 2 hours, or until firm.
Add cocoa powder to a small shallow bowl. Roll chocolate mixture into 1 inch balls and then roll in cocoa powder to completely coat.
Serve or place truffles back into the refrigerator to chill for 1 more hour if they need to firm up.