
Rinse beef shanks well to remove any blood or impurities. Drain well.
Peel the outer layer of the lemongrass stalks until you reach the pale central core. Cut into 3 to 4-inch lengths and with the back of the knife, lightly pound each piece. Set aside.
In a deep pot over medium heat, heat oil. Add beef shanks and cook, turning as needed, until lightly seared.
Add garlic and cook, stirring regularly, until softened.
Add water and bring to a boil, skimming scum that floats on top. When the broth clears, add onion.
Lower heat, cover, and simmer for about 1 1/2 to 2 hours or until meat is fork-tender.
In a small bowl, combine annatto powder with about 1/2 cup of the broth. Stir until annatto powder is dissolved and return broth to the pot.
Add tamarind soup base. Stir to disperse.
Add lemongrass, green jackfruit, kamias, and chili peppers. Continue to cook for about 10 to 15 minutes or until jackfruit pieces are heated.
Season with salt and pepper to taste. Serve hot.