Instant Pot: Set cooker to saute-high. Stovetop: Heat up to medium-high.
Add 4 tbsp oil and wait for it to heat up (approx. 30-60 seconds).
Cook the shank slices for aprox ~2 minutes per-side or until well seared. Once done; remove the cooked beef and place on a plate/bowl. Repeat steps with the rest of the shank slices until all are done (may need to add a bit more oil as you continue to sear the beef). Set aside until ready to use.
Drop in the sliced onions and minced garlic; mix/stir, cook for 1-2 minutes or until translucent and fragrant.
Add cut green onions, dried red peppers and shaoxing cooking wine; then deglaze the bottom of the cooker.
Add tomato paste and spicy bean paste; saute for ~30 seconds.
Pour both soy sauce and mix for ~30 seconds.
Place the seared beef back in the cooker. Mix and turn everything together until all is evenly coated/glazed.
Pour in the water. Then drop the rock candy (sugar), bay leaves and star anise in the cooker.
Instant Pot (8qt or larger): Pressure cook on high for 45 minutes and natural release for 30 minutes. Follow the manufacture instructions when preparing to removing the lid (as you release the pressure using the vent). NOTE: Cut the recipe in half if you have a 6 qt cooker and keep the same cook time.Stovetop (8 qt pot or larger): Bring broth to a boil. Turn down the heat to low-medium and cover the pot with a lid. Let it simmer for 3-4 hours or until the meat becomes cut with a spoon tender.
Remove lid, then discard bay leaves and star anise.