It seems that before we had ice cream, there was frozen custard. It is similar to ice cream but it uses egg yolk in the recipe (that caught my eye).
Frozen custard has the same minimum 10 percent milk fat requirement as ice cream with the addition of at least 1.4 percent egg yolks.
Frozen custard is, apparently, creamier and softer than ice cream. That's something I'll have to check out. Chocolate frozen custard sounds really good.