Wash and chop the tomatoes and crush them.
Scrub and wash the potatoes.
Cut them into chunks and set it aside.
Set the pressure cooker on medium heat.
Add the oil and cumin seeds.
As they crackle add the garlic, and onions to saute.
When the onions turn translucent, add the tomatoes.
Mix well and let them saute for a couple on minutes and cook off.
Add the salt, cumin powder, chilli powder, garam masala and saute well.
Once this masala mix starts leaving the sides and the water and the potatoes.
Pressure cook this for 3 whistles or on medium for 10 minutes.
Let the pressure release naturally.
Open the cooker and gently mash a few potatoes to add thickness to the curry.
Adjust the salt and mix well.
Stir in the chopped coriander leaves and mix well.