Passover is right around the corner! Join Molly Baz and Adam Rapoport in the Bon Appétit Test Kitchen as they make BA's best matzo ball soup. This soup is very schmaltzy, full-bodied, and flavorful. If you prefer a leaner, clearer broth, make the soup a day ahead, chill overnight, then skim the schmaltz from the surface of the soup before reheating. You can save the schmaltz to make the matzo balls or for another use. This recipe serves eight people generously (with two balls each) but could easily stretch to serve 16 smaller appetizer-sized portions. We ordered the steps so that you could make the stock and matzo balls simultaneously, but if you prefer to break up the work, you can make both the balls and stock a couple of days ahead.