When I’m idly googling hot fudge sauce, most of the recipes call for cream or evaporated milk, neither of which I keep around. Wouldn’t it be better if the main non-chocolate ingredient were melted ice cream, since you’re likely to have ice cream when you want hot fudge sauce?
Surprisingly, I didn’t find recipes– the closest was this one for Ice Cream Fudge. I made a half-recipe. It is not fudge– much closer to a truffle. But re-melted in the microwave, it’s not bad with ice cream. Not as liquid as real hot fudge sauce, but at least it doesn’t form hard little freckles of chocolate, like when you melt straight chocolate and put it on ice cream.
Might be worth trying it with a higher ratio of ice cream to chocolate.