Heat a shallow pan or wok over medium-low heat. Add oil and the star anise, frying for about 10 seconds to release the fragrance.
Add the pork belly cubes. Stir-fry over medium-low heat until they start to brown and release some oil.
Tip: Spread the pork evenly across the pan and let it sit for 30 seconds to 1 minute before flipping — this helps prevent sticking.
Move the pork to one side and add ⅓ of the chopped green onion. Stir-fry it in the oil, then mix together with the meat.
Move the pork to the side again and add the sweet soybean paste directly to the oil. Stir-fry the paste for about a minute before mixing everything together.
Add water, bring to a boil, and add the remaining green onion. Let it simmer until the sauce thickens and turns glossy.
Meanwhile, prepare your vegetables and cook the noodles. Serve the noodles topped with sauce, vegetables, and optional garlic. Mix well before eating.