Add the Massaman curry paste, coconut milk, coconut cream, ground cumin and ground coriander and water to the wok, and stir over a medium heat until they are all mixed together.
Add the chopped onion, sweet potato and chopped beef, stir and then simmer for 15 minutes
Add the sugar, cashew nuts, spring onions and kaffir lime leaves, stir and then simmer for 5 minutes
Add the fresh coriander and garam masala, stir and simmer for 5 minutes
Serve on its own with naan bread or serve with rice.