blanch spinach in boiling water for about 4 minutes,drain into sieve over another pan .Squeeze as much water as possible out of spinach with wooden spoon.
Bring water back to boil ,set spinach aside.Cut cross into tomatoes take spinach water of heat and add tomatoes ,leave in water for a few minutes.
Remove tomatoes and peel back skin , take out flesh discard seeds, keep tomatoes about 1/4 size.Discard water.
Heat oil in pan over medium heat and fry mustard seeds until they splatter,add onions ,garlic and ginger and fry for about 5 munutes stirring .Add the pre cooked but still slightly firn potato chunks,chilli powder salt and water,cook for 10 minutes.Add sspinach and tomatoes to the pan .Cover and simmer for 10 -15 minutes until potatoes are tender.
as an alternative to spinach this can be made with spring greens and use some fresh chopped chilli ,omit chilli powder.