This popular Belgian dish known as boulets liégeoise consists of beef and pork meatballs that are simmered in a gravy made with onions, flour, beef broth, and sirop de Liége. Sultanas are often added to the meatballs, and there are other versions of these meatballs as well - with cherries in Flanders, or with tomato sauce, mushrooms, and Madeira wine.