How do I avoid hot fudge turning my ice cream into a soupy mess? My pregnant wife's cravings have recently turned towards sweets, and this week it is banana splits, with a very specific formula: chocolate ice cream, banana, whipped cream, and hot fudge. 

It's not such an extraordinary recipe, I suppose, but the hot fudge is simply not a topping we keep in our house or really have a lot of experience with. So after picking up a jar of hot fudge topping, and zapping it in the microwave, per the instructions, I experienced the obvious result that has presumably been experienced by millions before: hot fudge melts cold ice cream.

Rather quickly, the sundae disintegrated into a soupy mess at the bottom of the bowl, with a rapidly decreasing scoop of ice cream bathing in the pool, and banana bits swimming about. It was not a pretty sight.

What means could I take to mitigate the fudge's effect on the ice cream, or are my wife's hopes and expectations just a dream in the shadow of this bleak reality?
I don't have any direct experience to share, but it seems a little logic may be applicable. I suggest that your hot fudge is too hot and your ice cream is not icy (cold) enough.

Rather than microwaving the fudge, try a hot water bath on the stove. Yeah, it's slower, but you also won't burn the bejeezus out of the sugar at the edges. Taste occasionally while stirring until you get that pleasingly warm mouthfeel. Stirring frequently* will help distribute the heat.

Alternately, microwave in small bursts, stirring* as you stop and taste.

*Sanitary practice compels me to advise you to use a fresh spoon every time you stir and taste in order to avoid contamination. But it's your house.

The hot part being taken care of, make sure your freezer is actually freezing cold. Don't take the ice cream out ahead of serving so it doesn't soften. Best way to scoop hard ice cream is to use a metal scoop dipped in very hot water. Cuts through like buttah.