Cook the spinach in the broth until tender. Drain and reserve broth. Mash out excess liquid. Cook pasta. Preheat a saute pan or heavy skillet over medium heat, add the oil or vegetable spray and saute the garlic, stirring constantly, until it is white. Don't allow it to brown. Add the spinach and nutmeg or mace, salt and pepper. Add the chicken pieces to the spinach, stir and turn and add a small amount of the reserved cooking broth. Stir and turn the spinach until it is hot, adding broth as necessary. Remove pasta and immediately drain. Add the shells into the spinach mixture and blend well. Serve immediately with Parmesan.