Makes about 3 dozen truffles
In a heavy saucepan, over low heat, melt chips with butter.Stir in cocoa until smooth. Add condensed milk and vanilla. Cook and stir until thickened and well blended, about 4 minutes. Remove from heat. Chill until firm enough to handle. Shape into 1 inch balls. Roll in desired coating.
Chill until firm. Store, covered in refrigerator.