For the ribs: Preheat the oven to 400 degrees F. Line a large roasting tray with foil and grease with the oil. Place the pork ribs in the roasting pan and rub the Chinese five-spice powder all over on both sides. Roast for 30 minutes.
Meanwhile, prepare the garnish: Cut the spring onion in half across and then cut each piece into really thin strips lengthwise. Put them into a small bowl of ice water, cover and sit in the freezer until ready to serve.
For the glaze: Put the ketchup, vinegar, soy sauce, honey, ginger and chili in a small pan; season with salt and pepper. Bring to a boil and then turn off the heat.
Once the ribs have been cooking for 30 minutes, remove from the oven. Brush half of the glaze over both sides of the ribs. Cover with foil and return to the oven for another 1 hour 30 minutes. Reserve the remaining glaze in the pan for later.
A few minutes before the ribs are ready, reheat the remaining glaze. Arrange the cooked ribs on a large serving platter and pour the warm glaze evenly over. Drain the spring onion garnish from the ice water. The onions should now have curled nicely. Scatter them over the ribs to garnish and serve at once.