Heat a large frying pan and add a little oil. Cook the burgers while mincing with a wooden spoon. Season with salt and pepper and mix well to ensure the seasoning is evenly distributed. Continue frying for 5–7 minutes until crisp and brown and broken down to a fine consistency. Drain the crisped meat in a sieve – this will help it stay crispy. Set aside.
Wipe out the pan and add a tablespoon of toasted sesame oil. Add the garlic, ginger and chilli. Fry with sugar and a pinch of salt for 2 minutes. Add the meat and stir to mix.
Add the fish sauce and heat through. Stir in the lime zest and juice, then add the green onions, stirring for 30 seconds. Turn off the heat.
Mix all the dressing ingredients together and adjust seasoning to taste.
To serve, spoon the minced burger mixture into the lettuce leaves, drizzle with a little dressing and serve.