Rinse the organ meats very well in plenty of cold water to remove all traces of blood.
To wash the intestines, rinse very well and invert, using a knitting needle as your guide. Continue rinsing and then rub with either lemon or salt. Chop the intestines and aside in refrigerator until ready to use
Rinse the head very well. Place in a pot with plenty of salted water and bring to a boil. Reduce heat to a simmer and cok slowly for about 2-3 hours, skimming the foam off the top and replenishing the water as needed. Remove the head, reserve the broth and strain, if desired.
Chop the organ meats. Heat the olive oil in a large, wide pot and saute the organ meats. Add the scallions and saute for a few minutes, until translucent.
Place the strained broth back into a large soup pot. Add the sauteed organ meats and scallions to the broth.Bring to a boil. Add the shredded lettuce, herbs, salt and pepper. Simmer the soup for about one hour, covered. Replenish the water as needed. There should be about 3 quarts total. Stir in the rice. Simmer until the rice is soft.
In a separate metal bowl, whisk together the eggs until very frothy. Slowly whisk in the lemon juice. Then, slowly 2 ladels full of the hot soup broth, careful not to get solids in the ladle. The hot broth should be added drop by drop. Return the tempered egg-lemon micture to the pot, with the heat turned off, and tilt the pot back and forth so that the avgolemono is evenly distributed. Do NOT cover the pot. Serve immediately.
“Genteel” Mageiritsa (without organ meats)
Instead of organ meats, use a lamb shank. Season it with salt and pepper, sautee it in olive oil in a large soup pot, add the scallions, then add water or meat stock. Season to taste. Cook all together for 2 – 3 hours or until the meat falls off the shank. Remove the shank, let it cool slightly, and remove and shred the meat. Place it back into the broth, together with the shredded lettuce and herbs. Cook together for 30 minutes, Add the rice. And follow the directions above for making the egg-lemon liaison.