Fill a big pot with ¾ full of water. Bring to a boil and gently drop the meat. Lower the heat to medium and let boil for about 10 minutes. Remove any dark scum that rises to the top. Discard the liquid and rinse the meat well in cold water to remove impurities.
Wash the pot and add the beef shanks. water, onion, salt and peppercorns then bring to a boil on medium-high heat. Skim off any scum that rises to the top as it boils and reduce the heat to low and simmer until the meat is tender.
Add the corn and cook for 5 minutes. Then, add the bok choy (or cabbage) and cook for another 3 minutes. Turn the heat off and add some chopped green onions (if using) before serving.
Combine the ingredients for the dipping sauce. Taste and adjust the amounts to your preference. Always serve the bulalo hot with steamed rice and the patis-lemon sauce on the side.
Notes
*Use the lower amount of water (10 cups) then add more if the broth is reducing too fast.
**If you want your bone marrow intact (and plump), carefully remove the marrow after the first 10 minutes of cooking. Set aside and replace before serving.
***Not all patis are created equal. Since I only use it sparingly, I splurge on the premium fish sauce. The Viet Huong Three Crabs brand has a very clean taste and smell, and not too salty.