Begin the first phase by seasoning the pieces of the lamb stew meat with salt and pepper, then add the flour to the meat and stir to coat the lamb.
Add olive oil to your skillet set on a medium high heat. Sauté minced onion and garlic, and chopped prosciutto in hot olive oil for around 3 minutes.
Increase the heat and add the lamb to the onion and prosciutto mixture. Brown the lamb on all sides and then stir in the wine until it evaporates. Then add the chicken broth and reduce the heat to a simmer. Cover the skillet and braise the lamb until it is nice and tender. From time to time check it and add additional broth if you feel the lamb is becoming too dry. This should take around an hour. However, continue to braise a little longer until the lamb is truly tender.
A few minutes prior to finishing braising the lamb, make the egg and lemon sauce. Combine egg yolk, lemon juice and zest, some marjoram and pepper in a small bowl and whisk well.
When the lamb if fully cooked and tender, turn down the heat to low or better yet even take it off the heat. Add the egg and lemon sauce and stir well to combine. If this sauce is added when there is heat, you run the chance of the egg scrambling...and we don't want that to happen! We want to achieve a nice and silky smooth sauce with the addition of the egg and lemon.
Garnish with some Italian parsley, and enjoy your succulent Abbacchio Brodettato!