Adding frozen, chopped spinach to your meatballs to “stretch” the meat further isn’t just kind to your pocket book — it also makes for a better meatball. The spinach brings moisture to the mix of beef and pork, which leads to a more tender and juicy meatball. (You can also exclusively use pork or beef if you prefer.) The spinach also accentuates the minerality of the iron-rich ground beef, adding savoriness without heaviness. This recipe has you brown the meatballs in a pot so that you can build the sauce with the flavorful drippings. If you’d prefer to cook the meatballs in the oven, roast them on the upper rack at 425 degrees until no longer pink, 11 to 14 minutes, then broil until golden-brown on top, 2 to 4 minutes before adding to the sauce. Be sure to scrape any drippings from the sheet pan into the sauce as well.