Cut the strips of ribs between the bones into individual riblets. Put the riblets, onion, ginger, water and ¾ teaspoon salt in a pressure cooker. Lock on the lid and bring to high pressure. Adjust the heat to maintain pressure and cook for 10 minutes, then naturally depressurize for 12 minutes. (Program a multicooker such as a 6-quart Instant Pot or T-Fal to cook on high pressure for 10 minutes. Unplug or turn off the machine then let naturally depressurize for 15 minutes.) Regardless of machine, finish by releasing residual pressure. (Without a pressure cooker, simmer the ribs with 6 cups water for 1 ¼ to 1 ½ hours, until tender. Add water as needed to ensure the ribs remain covered.)

Use tongs to transfer the riblets to a bowl. Add water to cover and let sit 1 to 2 minutes to cool. Drain and transfer to a rack set on a baking sheet to finish cooling for about 5 minutes, until lukewarm and relatively dry.

Strain the cooking liquid from the pressure cooker. Measure out 1 cup for this recipe and use the remainder for another recipe, such as a soup!

Beat the egg in a medium bowl. In a large bowl, stir together the cornstarch, five spice, and ¼ teaspoon salt. Spray or lightly oil the air-fryer rack. In 3 or 4 batches, coat the ribs in egg then dredge in cornstarch. Lightly pat to remove excess starch then put on the rack. Don’t let the ribs touch; you want to facilitate air circulation.

Preheat the air-fryer to 400F for 3 minutes. Air-fry the ribs for 8 to 10 minutes, turning midway when there are some brown spots. They’ll be crisp with lingering white areas due to the cornstarch. Don’t worry.

While the ribs air-fry, in a medium stainless-steel (or light interior) skillet over medium heat, toast the sesame seeds for 2 minutes, or until golden. Transfer to a small container. Warm the oil in the skillet over medium heat, then add the green onion, ginger, and star anise. Cook, stirring, for 1 minute, or until fragrant. Add the sugar, stir, and cook for 3 to 4 minutes, until it’s a rich caramel color.

Slide the pan to a cool burner, let rest for 1 minute, then pour in the reserved rib cooking liquid, soy sauce, and dark soy sauce. Stir to combine, then bring to a boil. Let cook for 2 minutes to develop flavor, then strain and return the liquid to the pan (or use a slotted spoon to remove the solids).

When the ribs are done, remove them from the air-fryer, let sit for 2 minutes to cool briefly. Return the seasoning liquid to a boil over medium-high heat, add the ribs, then cook, stirring constantly to get the reducing sauce to coat the ribs well. After about 2 minutes, when little free-flowing liquid remains, add the vinegar. Stir for about 1 minute longer to allow the ribs to absorb its tang.

Sprinkle on the sesame seeds, turn to coat, then transfer the ribs to a plate. Let cool for 5 minutes to develop flavor before eating as finger food. The ribs are also good at room temperature.