Make the spice packet: Place all of the whole spices: star anise, cinnamon, fennel seed, dried chilies, sichuan peppercorn, white peppercorn) into a cheesecloth and tie with a string. Set aside. Turn on the Instant Pot to SAUTE and wait until HOT. Add 1 tablespoon vegetable oil and place the beef shank in the pot to brown on all sides (about 3-4 minutes).
Add in the garlic, ginger, green onions and Thai chilies and saute until fragrant, about 1-2 minutes.
Add in the 5-spice powder and coriander powder.
Next, add in the dou ban jiang (broad bean paste), beef broth or water, soy sauces, and rock sugar. Stir until the sugar has dissolved. Drop in the spice packet and give it another stir.
Cover with the lid and set to MEAT setting for 40 minutes at HIGH PRESSURE.
Note: If you don't have an Instant Pot, simply add all the ingredients to a crock pot and braise for 2-3 hours on High or simmer over the stovetop in a dutch oven for 3-4 hours, until the beef shank is tender.
After 40 minutes, let the Instant Pot naturally depressurize. Remove the beef shank and let cool.
Strain the braising liquid into a sieve. Remove the spice packet and discard.
Save the braising liquid for beef noodle soup, or reduce the liquid to make a sauce in place of hoisin sauce. (Simply take the liquid, reduce it by about half, and add some cornstarch to thicken. Check the seasoning -- after reducing, the liquid may taste salty).
When the beef shank has cooled, use a sharp knife to cut into thin slices. Set aside.
You may have extra meat leftover, which would be great in a noodle soup.