Besides milk and cream, which substance is usually part of a classic stracciatella ice cream?

Apparently, in 1961, Enrico Panattoni was tired of stirring eggs into Stracciatella soup and came up with the idea for ice cream. His addition of liquid chocolate that froze into the gelato somehow made it reminiscent of the eggs in the soup. I'm having a hard time envisioning that, but Enrico and his customers understood.

https://en.wikipedia.org/wiki/Stracciatella_(ice_cream)#:~:text=It%20was%20originally%20created%20in,most%20renowned%20Italian%20gelato%20flavors.

Classic stracciatella gelato is made with milk, cream, chocolate, and sugar.

https://www.recipesfromitaly.com/stracciatella-gelato/#:~:text=The%20ingredients%20of%20Stracciatella%20Gelato,it%20requires%20TOP%20QUALITY%20INGREDIENTS.

Another recipe also calls for vanilla.

https://www.insidetherustickitchen.com/stracciatella-gelato/