Heat oil in a pan.
Splutter mustard seeds.
Add chopped onion and greenchillies and fry, till they turn golden brown.
Grind together ginger and garlic along with cashew and make a smooth paste.
Mix this paste and saute till the raw smell goes.
Add tomatoes into this and saute for some time.
Add masala powder, turmeric powder and chilly powder along with salt and mix well.
When a nice aroma comes, add the potato pieces along with 2 cups of water and allow it to boil.
When the gravy starts to thicken,Add the fresh cream into it and stir.
finally add chopped corriander leaves and remove from the flame.