Pound the both sides of the flank steak or beef slice. Be careful not to tear through the meat. The piece of meat should be large enough to hold the stuffing inside the roll, at least 8 x 11 inches or preferably larger.
In a mixing bowl, combine the ground meat, raw egg, grated cheese, breadcrumbs, minced garlic, chopped parsley, minced bacon, peas and salt and pepper.
Shell the hard-boiled eggs and slice off the ends to expose the yolk.
Lay the beef slice on the work surface so the width runs left to right. Lay the mortadella or cooked ham over the top of the meat slice then spread the ground meat mixture on top with the bottom of a spoon, but leave some space along the edges. Place the hard-boiled eggs in a row from end to end so the exposed yolks touch one another.
Have the butcher’s twine handy, then pick the beef slice from side nearest you, and snugly overlap the slice around the hard-boiled eggs. Fold in the outside ends and finish rolling the beef. Next, run the twine a couple of times around the length of the roll to hold in the ends. Tie a knot and then run the twine around the entire length and circumference of the roll. It is best to use as much twine as necessary to hold in the stuffing. Snugly tie the roll, but not too tight or it will squeeze out the stuffing.
Place a deep pan over moderately high heat and cook the onions until transparent, then add the meat roll and brown it on all sides. Lower the heat to medium then pour in the red wine and let it evaporate. Reduce the heat to low, add the bay leaf, beef broth or water (enough to immerse at least half of the roll) and then stir in and dissolve the tomato paste. Cover the pan and simmer for 30 minutes, Turn the meat to evenly brown the roll.
When the farsumagru is finished cooking, remove it from the pan and let it cool on a cutting board. Salt and pepper the remaining sauce and simmer a minute or two longer.
Untie the roll and slice into medallions. Ladle the sauce onto a serving dish or individual dinner plates and arrange the farsumagru medallions on top.