Wash and soak bones in cold water for 5-6hours. Rinse and Parboil for 6min. Rinse and drain.
In a big stock pot, add 2 gallons of water and bones. Bring to boil and medium heat simmer for about 3 hours. Skim all the fat floating on top of the broth.
Meanwhile submerge and soak flank steak in cold water for about an hour. Rinse and pat dry.
Into the stock pot, add flank steak, garlic, Chinese scallion, ginger, and peppercorn. Close lid. Bring to boil then med heat simmer for about an hour, or until fork can easily pierce the meat. Skim all the fat floating on top of the broth and discard. Turn off heat.
Meanwhile, make meat marinade, set aside.
Take out flank steak and let it cool. Cut into big chunks then shred with hand. Add the meat and meat marinade into a bowl and toss them together for 1-2min. Taste and add more as needed.
Pour broth into a large soup bowl and add marinated meat. Can also garnish with fried egg strips, scallions. Serve with hot sticky rice and sea salt on the side.
**Bones can be discarded or can be reboiled 2 more times to produce additional broth. Just add water and boil similar method as above.