Clean and wash the bull organ and oxtail, place in a large pot.
Pour enough water to cover meat bring to a boil and let boil for 5 to 10 minutes.
Remove from heat and discard water, wash off all scum from the meat and return to the pot. Pour fresh water to cover meat at about 2 inches.
Add in the whole garlic, sliced ginger, quartered onion peppercorns and sibot mix herb.
Bring to a boil and simmer for 4 to 6 hours at low to moderate heat.
Add more water as necessary.
When done remove pot from heat separate the broth from the meat. Using a sieve strain off all solid residue from the broth.
Discard residue and keep aside broth.
Slice the bull organ and oxtail into thin slices.
Discard oxtail bones.
In saucepan sauté chopped garlic, ginger, and onion.
Add in the sliced meats and continue to stir-fry for 2 to 3 minutes.
Add in the fish sauce and stir cook for another 1 to 2 minutes.
Add in the reserved broth, bring to a boil and simmer for 10 to 15 minutes.
Season with salt and pepper to taste.
Add in the chopped spring onion and cook for another minute.