Heat the oil in a wok. Add the ginger, garlic and chilli and cook for 2 minutes. Add the turkey mince and fry, stirring, for 5 minutes.
Stir in the fish sauce and brown sugar. Cook for a further 5 minutes until cooked through – the mince should be dark and sticky with no pink colour remaining. Stir through the coriander. Spoon a little of the mince mixture into each lettuce leaf to serve.