Combine the lemongrass, ginger and galangal in a food processor and blend to a fine paste.
Add the onion, chilli and garlic and blend again until a coarse paste forms.
Heat the oil in a heavy-based saucepan over medium heat, add the paste and fry, stirring, for about 8–10 minutes, or until the oil separates into a gorgeous red.
Add the beef and fry, turning occasionally, until lightly browned all over (5–6 minutes).
Add the coconut and fry for another minute, then add the coconut milk, sugar and 2 cups (500ml) water.
Bring to the boil, stirring frequently to prevent curdling, then reduce the heat to low and leave to bubble gently, stirring now and then, until the beef is tender and the coconut milk much reduced (about 1.5–2 hours).
Once the coconut milk begins to turn to oil, remove the beef from the saucepan.
Continue to stir the sauce (be careful, it will spit) until it is almost evaporated and almost dry, about 5–10 minutes.
Return the beef to the saucepan, stir gently, season to taste with salt and serve with rice.
