Rinse the pork tails, remove the hair, and cut them into smaller chunks.
Add cold water and pig’s tail to a large saucepan or pot. (Make sure the pig tails are submerged.)
Bring to boil and drain the water. It’ll take about 10 minutes. Rinse the pork tails to remove the foam and small particles.
In a large pan over medium-heat, add oil, garlic, ginger and green onion. Stir fry for about 1 minute until fragrant.
Add cooked pig tail chunks, star anises, sugar, soy sauce, cooking wine to the pan.
Add water to make sure the liquid covers the pork tail completely.
Bring to boil, and then lower the heat.
Cover the lid and simmer for about 1 hour until the pork tail has become completely tender.
Remove the lid. Turn the heat to high, cook until the sauce has thickened. If you have a lot of liquid in the pan, it may take a while. You can add cornstarch slurry (mix 2 tablespoons of cornstarch and water). This will thicken the sauce much faster and make it sticky.
Season with more salt if needed and serve immediately.