Heat the oil in a frypan. Add the onion and garlic and cook until softened, about 4 minutes. Add curry powder and stir in for another minute.
Add chicken stock and bring to a simmer. Add prawns and lime juice and simmer until prawns are just cooked through, about 3 minutes. Stir in the coconut milk and season with salt and pepper. Serve over rice, garnished with coriander.