Beat the butter and brown sugar with an electric mixer in a large bowl until smooth. Beat in the vanilla extract. Add flour, alternately with sweetened condensed milk, beating well after each addition. Fold in the chocolate chips and toffee bits; mixing just enough to evenly combine.
Using a small cookie scoop, make 1-inch balls and place them on waxed paper lined baking sheets. Refrigerate until firm, about 1 hour.
Melt the chocolate coating in a microwave-safe glass or ceramic bowl in 30-second intervals, stirring after each melting, for 1 to 3 minutes (depending on your microwave). Do not overheat or coating will scorch. Dip the dough balls in the chocolate coating, allowing any excess to drip off. Place on waxed-paper lined baking sheets and sprinkle the truffles with additional toffee pieces. Refrigerate until firm, about 15 minutes. Store in the refrigerator.