Line 2 cookie sheets with wax paper. Set aside. Mix butter, sugar and sweetened condensed milk in large mixing bowl. Add coconut, pecans and vanilla extract; mix well, using a sturdy large spoon. Chill until firm enough to handle. Form into small balls and place on prepared cookie sheets. Chill until very firm. Melt chocolate chips in microwave, stirring often to ensure they don't burn. Using a toothpick or candy dipper, dip balls into melted chocolate and place back on wax paper. Let cool until set. Store in airtight container.