Slice the pork tenderloin on a diagonal into about 8 pieces. Slightly pound each piece to 1/4 inch thick and season each slice of meat with salt and freshly ground black pepper. Place a couple of sage leaves on each piece of meat and then wrap it in a slice of prosciutto.
Preheat a large skillet over medium-high heat with 2 tablespoons EVOO, about two turns of the pan. Working in two batches, sear the wrapped pork until cooked through, about 3-4 minutes per side. Add another tablespoon of oil to pan before cooking the second batch. When the first batch is complete, reserve the meat to a platter and cover with foil to keep warm while the second batch cooks.
While the pork is cooking, preheat a second large skillet over high heat with 3 tablespoons EVOO, about three turns of the pan. Add the smashed garlic to the pan and cook until lightly golden and aromatic, about 1 minute. Add the spinach to the pan and saut until tender and wilted, about 4-5 minutes. Season with salt, freshly ground black pepper and a few grates of fresh nutmeg.
To serve, divide the spinach among four plates and top each with two pieces of the wrapped pork.