Punjabi Potato Patties

1)peel and dice the potatoes,put them in a pan and cover with cold water.cover bring to the boil and boil gently for 10 minutes,until the potatoes are tender but not disintergrating.
2)peel and roughly great the onion onto double thicckness of kitchen paper.squeeze out any juice then put it into a bowl.add the chilli,garam masala.
3)squeeze 2 tsp of lemon juice into the onion.rinse and dry the coriander.reserve a few springs for garnish,chop the remaining leaves andadd to the bowl.
4)drain the potatoes,add them to the onions and mash roughly together.shape into eight patties,each about 2in wide.
5)heat the oil and butter in a large frying pan until sizzling,then fry the patties for 2-3 minutes on each side until crisp and golden.
6)drain the patties on kitchen paper and serve them hot,garnished with chutney or ketchup if desired.or set aside to eat cold later.