Authentic Boulets Liégeois: large tender pork and beef meatballs browned in butter and simmered in a luscious sweet-sour sauce of caramelised onions, Sirop de Liège, and raisins.
Mix the minced meat, soaked breadcrumbs, egg, parsley, salt, and pepper. Shape into 6 large round meatballs (boulets). Brown in butter in a Dutch oven for 8 minutes until golden on all sides, then set aside.
In the same pan, cook the sliced onions over medium heat for 10 minutes until soft and golden brown.
Deglaze with cider vinegar. Stir in the Sirop de Liège, hot beef stock, and drained raisins. Bring to a simmer, stirring until the syrup melts into a rich brown sauce.
Return the meatballs to the bubbling sauce. Cover and simmer gently for 25 minutes until cooked through and coated in the glossy sweet-tart sauce, serving with Belgian frites.