Sprinkle sugar over beef, then drizzle with wine. Leave to marinade for 20 minutes.
In a food processor, process lemongrass, ginger, garlic, cashews, chilli, coconut oil and 200ml of the coconut milk. Slowly add more coconut milk, one spoonful at a time until the mixture becomes loose paste.
Heat oil in a skillet over high heat. Brown beef all over, add the paste, curry powder, then pour remaining coconut milk in. Transfer to a slow cooker and cook on high for 4-6 hours. Season to taste with salt and pepper.
Serve with coconut rice, hot paratha (optional), topped with cashews and coriander.