FRENCH ONION MATZA BALL SOUP Serves 6 to 8 In February I had the pleasure of collaborating with chef olivia_ostrow on a dinner in Miami where we served French onion matza ball soup to reflect our shared cooking style. I came home and developed this rich onion soup recipe–bolstered with white wine, beef stock, and balsamic–which I highly recommend either for a slightly unconventional seder night, or during Passover week to serve with leftover matza balls. The secret ingredient here is time; let those onions get meltingly soft and sweet over low heat; get those podcasts on, call your best friend, or organize your kitchen so you can stay nearby and stir. (If you have homemade beef stock you’re batting 100!) The rest is truly simple, and one of the best soups you’ll ever taste.  ⅓ cup olive oil, schmaltz or beef fat  4 pounds yellow onions, cut into ¼-inch slices 1 tablespoon kosher salt, plus more to taste freshly ground black pepper to taste 1/2 cup dry white wine 6 cups beef stock 3 s...