Solid + solid = liquid: Chocolate shell topping for ice cream

When I was growing up, one summer treat I really looked forward to was visits to Dairy Queen. I favoured Blizzards (to this day, I prefer ice cream with mix-ins), but I thought dipped cones were fascinating, even though I never ordered them. How did they put ice cream – upside-down, no less – into melted chocolate without turning it into a puddle?

It wasn’t until I started learning more about chocolate that I began to understand just how impressive a trick it was. The melting temperature of cocoa butter is around 34°C, about the same as a hot summer’s day. We all know just how quickly ice cream melts under those conditions.

The answer, of course, is that it isn’t chocolate… or, at least, it isn’t just chocolate. Instead, the dip is a mixture of chocolate with another type of fat (often coconut oil) that takes advantage of a phenomenon called eutectics. The melting point of a eutectic mixture is lower than that of the individual components, much like salt is used to lower the freezing point of ice in winter.

Both cocoa butter and coconut oil are solids, but when you melt them together, the resulting mixture is a liquid at (or just above) room temperature. At ice cream temperature, though, it’s a solid, which is what makes the hard shell. Because the dip’s initial temperature is so much cooler than melted chocolate, it doesn’t melt the ice cream as quickly. Plus, it’s more fluid than chocolate, which helps produce a thinner shell.

Conveniently, coconut oil is easily found at health food stores these days, so you can even make your own chocolate shell mix. With the summery weather we’ve been having lately, I decided to give it a try, using this recipe; I made the plain version, but she also offers directions for flavoured versions.

Rather than just pouring it over my ice cream, though, I assembled the tartufi shown above. (Equipment nut that I am, I can’t help but think they’d look a lot better if I had large hemispheric moulds.) Vanilla ice cream with cherry preserves in the centre, a chocolate shell and a bed of peanuts… it tastes just like a sundae!

What role did chocolate shell topping play in your childhood?

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