Cook, stirring often, until the farro has absorbed the liquid. Continue cooking the farro, adding the stock a ladle- or cupful at a time and allowing the grains to absorb the stock each time before adding more, until the farrotto is creamy and the grains are tender and have burst open, 45 minutes to 1 hour.
Add ½ ladleful of stock and cook for a few minutes, until the farrotto is a loose and spoonable consistency, like porridge, not so runny that you couldn’t eat it with a fork. If the farrotto gets too dry, add more stock or water.
