Lay the flank steak on a chopping board with the grain of the meat running parallel to the right edge of the board.
Place your free hand flat against the top of the steak and using a very sharp knife, insert the knife along the trimmed edge of the steak. Keep the knife horizontal and slice lengthways through the middle of the flank, taking care to not cut all the way through the end seam of the meat.
Season both sides of the flank well with salt and freshly ground black pepper.
Evenly spread the cream cheese and garlic over the inside of the butterflied beef.
Place the mozzarella slices over the meat in rows and top with chopped artichokes and baby spinach and tightly roll up the flank letting it rest seam-side down to keep it closed.
Tightly tie about 6 or 7 pieces of butcher’s string around the flank roll to secure the stuffing.
Using a sharp knife, evenly slice the meat between each piece of string wiping the knife with a damp cloth after each slice.
Heat a splash of olive oil and a knob of butter in a large frying pan over a medium-high heat and cook the stuffed flank medallions in batches, spooning the butter over the meat, for about 3 minutes on each side or until the cheese is melted and the beef is cooked to your liking.
Serve the gooey spinach and mozzarella flank medallions with roast vegetables and don’t forget to remove the string before serving.