Cut off the ends and string some young string-beans. Cook them in
salted water, then drain them well. Put them in a saucepan with some
butter, parsley, and chopped onion. Be careful to add occasionally
some broth if the beans dry up before they are completely cooked. Boil
slowly, and a few moments before taking them off the fire add the
yolks of one or two eggs (according to the quantity of beans) well
beaten up with a little water, the juice of a lemon, and some grated
Parmesan cheese. Stir from time to time, and never allow them to boil,
or the eggs will set. To keep the beans a good color put a pinch of
soda into the water with the salt.
Source:
Simple Italian Cookery 
