Place beef, 1 tin coconut milk, stock, cardamom pods, cloves, star anise, sugar, fish sauce and tamarind in a saucepan and bring to the boil. Simmer uncovered about 1 - 1 1/2 hours until beef is tender.
Strain out beef, reserving the sauce. Discard the cardamom and star anise.
Place curry paste in a saucepan over low heat, stirring until fragrant. Add remaining coconut milk, extra tamarind and stock. Bring to a simmer, stirring until smooth. Add beef, onions, kumara and 1 cup of the reserved sauce. Simmer 30 minutes or until vegetables are tender.