Put the beef shank and marinade ingredients into a Zip-Lock bag or food container, seal it, shake well and place in a fridge for one day.
Rinse off peppercorns and place beef shank in the Instant Pot along with all ingredients.
Close the lid, and turn the pressure valve to the "Sealing" position. Press the [Pressure Cook] button and set to 35 minutes of cooking time.
When it is done, wait another 10 minutes. Slowly release the pressure then open the lid. Take out the cooked beef shank and place into a clean container. Chill for 4 hours, slice and serve.