Gently melt the light muscovado sugar with two-thirds of the fish sauce in a heavy based saucepan, stirring all the time.
Allow to cool a little then transfer it to a bowl and combine it with the garlic, shallot, palm or caster sugar, the remaining fish sauce and salt.
Add the minced pork, mix thoroughly, then cover and leave to stand for 3 hours.
Shape the minced pork into 20-24 flat little patties, about 1 inch in diameter, place them under a preheated grill and cook for 3-4 minutes on each side, until cooked through. The patties are also very good cooked on the barbecue.
To serve, divide the noodles between 4 warmed bowls, add the pork, torn lettuce leaves, bean sprouts and herbs.