Preheat oven to 350°.
In large saucepan, over low heat, melt chocolate and margarine with sweetened condensed milk; remove from heat.
Add biscuit mix and vanilla; with mixer, beat until smooth and well blended.
Cool to room temperature.
Stir in chips.
Shape into 1 1/4-inch balls.
Place 2 inches apart on ungreased baking sheets.
Bake 6 to 8 minutes or until tops are slightly crusted (do not overbake).
Store tightly covered at room temperature.