Heat the oil in a large, nonstick frying pan or wok over a high heat, add the ginger, chilli, lemon grass and lime leaves and fry for 1 minute.
Add the pork and stir-fry for 4—5 minutes until slightly browned and cooked through. Add the fish sauce and lime juice to taste then remove the pan from the heat.
Cut the cucumber into very fine strands and arrange on serving plates next to a lettuce leaf. Serve the pork on the lettuce, garnished with the chopped peanuts, herbs and red chilli.