Source: Libro de arte coquinaria by Maestro Martino de Como, 15^th century

Original Recipe:
Frictata.
Battirai l'ova molto bene, et inseme un poca de acqua, et un poco di lacte per farla un poco più morbida, item un poco di bon caso grattato, et cocirala in bon botiro perché sia più grassa. Et nota che per farla bona non vole esser voltata né molto cotta. Et volendola fare verde, prendirai slmilmente le cose sopra ditte giognendoli del suco de queste herbe, cioè vieta, petrosillo in bona quantità, borragine, menta, maiorana, salvia in minore quantità, passando il ditto suco; poi cavarai piste le herbe molto bene per la stamegna. Et per fare in un altro modo frittata con herbe, prendirai le sopra ditte herbe et tagliate menute le frigerai un poco in un bon botiro o oglio, mescolandole con l'ova et l'altre cose sopra ditte farai la frittata et cocirala diligentemente che sia bene staionata et non troppo cotta.

Translation: (from The Art of Cooking: The First Modern Cookery Book)
Beat the eggs well together with a little water and milk to make the frittata softer; likewise, add some good cheese that has been grated and cook the frittata in good butter to make it more fatty. Not that, for it to be good, it should not be stirred or overly cooked. If you wish to make it green, take the things mentioned above and add the water from the following herbs: chard, a generous amount of parsley, borage, mint, marjoram, and a lesser amount of sage, passing through a stamine to obtaine their water; then remove the herbs that will have been crushed in the stamine.
Another way to make a frittata with herbs is to take the above herbs, finely chop, and fry in good butter or oil, and then by mixing them together with the eggs and the other ingredients mentioned above, you make the frittata which should be carefully cooked when well seasoned, but not overcooked.

My Interpretation:

Chop herbs fine and saute in olive oil. Reduce to low heat. Whisk together eggs & milk. Pour into cooked herbs. Finish under broiler, if needed to set eggs.

Note: For purposes of feast saute the herbs, let cool. Stir into beaten eggs. Cook egg/herb mixture in batches. Place in warming oven until ready to serve.

Works Referenced:
Libro de arte coquinaria, Maestro Martino de Como, Digital version: Valeria Romanelli, 7/2004. http://www.uni-giessen.de/gloning/tx/martino2.htm

The Art of Cooking: The First Modern Cookery Book, Translated by Luigi Ballerini, Jeremy Parzen, Stefania Barzini, University of California Press, 2005
- A translation of the work of Maestro Martino of Como, 15^th century