Boil 6 cups water in a cooking pot.
Put Ox bat and balls. Continue to boil for 15 to 20 minutes. Remove from the cooking pot and wash with running water. Discard the water.
Pour 6 cups water in a cooking pot. Let boil. Add sibot herb mix and lemongrass. Cook for 5 minutes.
Add bat and balls into the pot. Continue to cook for 3 to 4 hours or until tender. Note: you can use a pressure cooker to tenderize it quickly. Add water as needed.
Remove the meat from the pot. Let it cool down and then slice into smaller pieces. Filter the liquid using a kitchen sieve to separate the solid ingredients. Set aside.
Heat oil in a cooking pot. Saute garlic, onion, and ginger until garlic browns and onion softens.
Add the sliced bat and balls and chopped Thai chili. Saute for 2 minutes.
Pour the filtered liquid and add beef broth. Let boil. Cook for 20 minutes.
Season with fish sauce and ground black pepper and add sugar. Cook for 5 minutes more.
Make the soup thicker by pouring a mixture composed of cornstarch and water. Stir.
Transfer to a serving bowl. Serve.
Share and enjoy!