Heat a deep pan, add oil and butter, and cook onion, garlic, and lemongrass until softened.
Stir in the rice for one minute, then add the stock and simmer.
Cover and simmer gently for 15 minutes until the stock is absorbed.
Mix in the lime zest, juice, and coriander, then season with salt and pepper.
Rub steaks with oil and coat thoroughly with a mixture of potato flour and star anise.
Fry steaks in hot olive oil for 2-3 minutes per side, then rest for 3 minutes.
Simmer rice wine vinegar and sugar in a pan, then add soy, chilli, and ginger until thickened.
Serve thick slices of steak over the pilau rice and drizzle with the chilli sauce.