Wash the kale leaves and chop it small, keep aside.
Wash and peel the onions and slice it evenly, keep aside with the kale.
Wash the potatoes, peel and cut into even medium sized cubes, keep this separately.
Wash the tomatoes and chop in small pieces, keep this aside with the potatoes.
Heat oil in a pressure cooker and add the mustard seeds.When the mustard seeds splutter, add the broken dried red chilies and fry for a few seconds.
Add the chopped onions and kale leaves to the pressure cooker (make sure the leaves are dry and no water content left) and saute in medium heat for 2 to 3 minutes.
Add salt, crushed ginger and garlic, stir well and saute for another 2 more minutes.
Add the chopped potatoes and tomatoes to the cooker, add a bit more salt if needed, and stir well the contents, saute everything together for another 2 more minutes.
Add the spices - turmeric powder, red chili powder, garam masala powder, black pepper corns and cumin seeds powder to the pressure cooker, stir the contents well and saute for one more minute.
Add the water to the pressure cooker, stir everything well.
Close the pressure cooker and cook in medium heat for about 7 to 8 minutes or until 2 to 3 whistles come.
Wait for the pressure cooker to cool down.Once the pressure cooker is cooled enough, open the cooker, stir the contents and see if the potatoes are cooked and soft and if the gravy is thick enough.
As I mentioned earlier, if you wish you may add ¼ cup of coconut milk or heavy cream for extra flavor and to make the curry more rich and delicious. Just mix the cream and cook in low heat for another 1 minute. I didn't add any cream or coconut milk and it was yummy as we enjoyed it with chapathi. Serve the hot kale potato curry with rice or as a side dish with Indian flatbreads like chapathi, poori or South Indian pancakes like appam.