Soup alla Modanese is a type of soup made with stock, spinach, butter, salt, eggs, Parmesan cheese, nutmeg and croutons.

One pound of spinach is washed in five or six waters, then chopped very fine and mixed with three ounces of butter and some salt. The mixture is then heat and cooled, passed through a hair sieve and combined with a tablespoon of grated Parmesan cheese, two eggs and a small amount of nutmeg, then combined with boiling stock. Sometimes, hot coals are placed on top of the lid to the saucepan so that the eggs will curdle and thicken the soup, which is served with fried croutons.

References

Source: The Cook's Decameron: A Study In Taste, Containing Over Two Hundred Recipes For Italian Dishes from a project that puts out-of-copyright texts into the public domain. This is from a *very* old source, and reflects the cooking at the turn of the last century. Update as necessary.