I think Janet was looking for this, not sure if she ever got an
answer, but I just found this....sounds good to me!

HARD CHOCOLATE SAUCE-DAIRY QUEEN STYLE
1 pkg. (6 oz.) chocolate
chips
1/2 stick butter or margarine
1/4 c. Mazola oil

In a double boiler melt chips and butter together.When melted add oil.
Pour over ice cream and it will harden.