How do I avoid hot fudge turning my ice cream into a soupy mess?

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.

Eat it faster.

Seriously. I am a huge fan of homemade hot fudge and much of the appeal is the contrast between the cold and the hot. Freezing your ice cream more solid will help but insufficiently heating the chocolate won't. If the fudge gets too cool it sets up into one solid chewy chunk.

Perhaps your best solution would be to serve smaller portions that can be consumed before the fudge and the ice cream reach equilibrium and the magic is lost.

I think isolating the fudge could be a good way to fix this. It might complicate your dish, but it might add both to the presentation as well as to the texture of the ice cream.

Try getting hold of or make your own biscuit rolls (I don't know the name). Fill these up with hot fudge. The biscuit will act as isolation keep the texture of both the ice cream and the fudge. In this way the only time the two will get in contact with each other is when one breaks up the biscuit to eat it.

If biscuits doesn't cut it, chocolate tubes or similar could do the same trick.

When I was a teen in a rollerskating ice cream parlour, we had to get sundaes out quick with hot fudge.

Most of the fudge was swirled around the glass container (somehow colder than porcelain) and only a bit on top before a blast of cream and a shower of nuts.

My parents always enjoyed making hot fudge but had similar issues to you. So they found very small bowls and now serve the ice cream in normal sized dishes (with any additional non-melting toppings) and provide a small side dish of fudge.

Two great benefits with this method.

1. Ice cream doesn't melt/Fudge doesn't cool off as quickly.
2. Every person gets to enjoy as much or as little fudge as they like.

Hope you can find a way that works for you.

It's a simple matter of thermodynamics. Consider the variables:

• temperature of ice cream, T_ic

• temperature of fudge, T_f

• heat transfer coefficient, h

• heat transfer surface area, A

I'll leave the derivation of the heat transfer equation as it pertains to sundaes as an exercise for the reader, but it's intuitive that you have a number of options, including:

• colder ice cream

• not quite so hot fudge

• modifying the heat transfer coefficient, such as by adding insulating materials or using an ice cream with lower thermal conductivity (it'd be interesting to study the effect of overage on heat transfer)

• decrease the area of contact between fudge and ice cream; it's a good be that sundaes are traditionally served in tall, narrow glasses for just this reason

I’d say scoop the ice cream and then lay it on a sheet pan (cookie sheet if you prefer that name lol) scooped out for like ten mins or so then melt the fudge let it sit for a min or two assemble the sundae and let her pour it on