Put the lemongrass, garlic, pepper and shallots into a food processor or mortar and pestle and process or pound to form a smooth paste.
Heat the oil in a 6 litre heatproof casserole dish over a medium heat, add the beef in batches and cook until browned. Remove.
Add the lemongrass mixture and cook for 3 minutes or until fragrant. Return the beef to the pan, add the coconut water, coconut milk, fish sauce and simmer, covered for 1 hour.
Add the potatoes and baby corn continue cooking for 20 minutes, then add the beans and cook, covered for a further 10 minutes or until the beef is tender and the potatoes are soft.
Steam the baby bok choy in a steamer above simmering water, ensuring the base of the steamer does not come in contact with the water. Serve lemongrass coconut beef with the steamed baby bok choy and steamed Jasmine rice.