In a large bowl, use electric mixer to cream together butter and brown sugar. Add vanilla. Beat in flour, 1 cup at a time, until it is incorporated and you no longer see chunks of brown sugar (if you spot any, just squish them). Beat in sweetened condensed milk and mix until well-combined. Stir in 1 cup of chocolate chips.
Cover bowl and refrigerate until dough is firm (at least 1 hour- maybe more... you want the dough to be quite firm). Use a small cookie scoop to scoop out heaping Tablespoonfuls, roll into balls and place on a waxed paper-lined cookie sheet. Place all of the rolled balls back into the refrigerator until you are ready to dip them in chocolate.
Melt chocolate bark in a glass bowl- easiest to do in the microwave in 30 second bursts, stirring after each heating time, until smooth. Use a spoon to help you dip the chilled dough ball into the chocolate and roll it around to cover all sides. Place it on a waxed paper-lined platter. Sprinkle with any desired toppings. Repeat with the rest of the dough balls. They'll begin to set pretty quickly. Keep them refrigerated until ready to serve.