Preheat the oven to 150°C (gas mark 2; if using a fan oven, set to 130°C).
Pat 1.6 kg bone-in beef short ribs dry with kitchen roll. In a small bowl, mix together 1 tsp salt, 1 tsp black pepper, 1 tsp garlic powder, 1 tsp onion powder and 1 tsp smoked paprika. Rub the spice mix evenly all over the ribs.
Heat 1 tbsp olive oil in a large, ovenproof casserole dish over a medium–high heat. When the oil is shimmering, sear the ribs in batches for 2–3 minutes on each side, until golden brown. Remove the ribs and set aside.
Return all the ribs to the casserole dish and pour in 240 ml beef stock around them. Cover tightly with the lid or a sheet of foil. Transfer to the oven and cook for 2½ to 3 hours, or until the ribs are very tender.
Carefully remove the casserole dish from the oven and drain off most of the cooking liquid, leaving about 60 ml. Brush the ribs all over with 240 ml barbecue sauce. Increase the oven temperature to 190°C (gas mark 5; if using a fan oven, set to 170°C) and bake uncovered for 20 to 30 minutes, or until the glaze is sticky and caramelised.
Leave the ribs to rest in the casserole dish for 10 minutes before serving.