For the ribs, place the tomato ketchup in a large shallow dish with the soy sauce, honey, ginger, garlic, sherry, star anise (if using), ketjap manis and rosemary. Mix thoroughly to combine.
Add the ribs. If time allows, cover and chill for up to 24 hours.
Place ribs in a large, deep pan. You may have to cut the ribs in half to get them to fit. Pour over the tomato ketchup mixture and then add enough water to completely cover the ribs.
Bring to a simmer, then cook over a medium heat for 45 minutes to one hour until completely tender.
Preheat the grill. Remove ribs from the sauce and arrange ribs on a grill rack. Place the sauce on the hob over medium heat and reduce down until it has a sticky coating consistency.
Place the ribs under the preheated grill for about eight minutes on each side, basting or painting the ribs with the reduced marinade occasionally. Alternatively cook on a barbecue.
For the potato wedges, preheat the oven to 200C/400F/Gas 6. Prick each potato all over with a fork and rub with a little of the oil. Place potatoes directly on the oven shelf and bake for 40-45 minutes or until slightly softened when squeezed, then leave to cool.
When cool, cut each potato in half lengthways and then into quarters. Slice away a bit of the flesh, leaving a layer of potato at least 5mm/1/4in thick on the skin. Brush all over with the remaining oil.
Place the polenta, parmesan, rosemary, salt and a generous grinding of black pepper in a bowl and mix together. Add the oiled potatoes and toss with the polenta mixture. Shake off any excess, then arrange in a single layer, skin-side down, on a wire rack set on a roasting tray.
Place in the oven and bake for 30 minutes, turning halfway through, until crisp and golden-brown.
To serve, cut the ribs into single-rib portions and arrange on a large platter. Scatter over the spring onions. Serve the potato skins and mini sweetcorn on the side or in separate bowls with plenty of napkins and finger bowls on hand for sticky fingers.