Put the minced pork in a bowl. Wipe the mushrooms then slice them thickly and chop finely in a food processor. Add to the pork with the soy sauce and fish sauce.
Put the chillies, coriander, lemon grass, garlic and shallot into the food processor and chop as finely as you can. Add to the pork with 1/2 tsp salt and several grinds of black pepper. Mix all the ingredients well.
Using floured hands press the mixture into 6 flat patties about 3 inches in diameter. Set aside.
Heat the oil in a large non stick frying pan and when hot add the patties. Cook for 1-2 minutes then turn with a palette knife and cook on the other side for a minute. Reduce the heat, cover the pan and continue to cook for 4 minutes. Drain on kitchen paper.
While the patties are cooking split the buns and toast the flat sides. When golden spread lightly with the chutney then sandwich the hot patties between them. Serve immediately.