Arrange rib racks in a roasting pan. Combine sherry, soy sauce, sesame oil, mango chutney, honey, green onions, fresh ginger and garlic cloves in a bowl. Pour marinade over ribs turning to coat.
Cover and refrigerate overnight. Turn ribs once during marinating.
Place one oven rack in the upper third of the oven and 1 rack in the bottom third. Drain ribs and pour marinating liquid in a saucepan. Bring to a boil and remove from the heat.
Arrange each rack of ribs on a baking pan. Place each baking pan on each rack in oven. Bake ribs in preheated oven to 300°F (150°C) until they are very tender, basting them every 25 minutes with 1/3 cup of the marinade, for approximately 3 hours. If necessary cover edges of ribs with foil to protect from burning.
Cut between bones, to separate ribs and serve.