I wouldn't think you'd need to parboil the spinach, GA. It cooks in about a minute or two, max. When I do it, I saute a little garlic in olive oil then throw in a huge bunch of spinach and put the lid on the pan. In just a few minutes, the spinach is done. Sometimes I toss in a shake of balsamic, although it doesn't need it.
Many times when I make a pasta dish, I put it over a bed of sauteed spinach. I also toss it into pasta sauce, eggs and everything else, practically! It's a great way to get nutrients. If I add just a bit into meals that way, it lasts a lot longer. It seems like a giant bag of fresh spinach makes about a cup when it's cooked!