Heat 1 tablespoon of oil in a large sized pressure cooker (6 quart is enough) and add the sliced onions.
Saute the onions in medium heat for about 7 to 8 minutes until the onions are lightly sauteed.
Add the garlic and saute for another 2 minutes.
Add the tomatoes and stir fry the contents for another 2 minutes.
Add the potatoes and black beans, mix everything well.
Add the 3 cups of water and salt, mix the contents.
Now add all the spice powders and mix again.
Close the pressure cooker with lid, and switch on the stove. Once the steam starts coming, cook for about 10 to 12 minutes of time or until 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 in medium heat, simmer the contents for about 6 to 7 minutes or until the gravy is just enough. In case if the gravy is less for your preference, you may add little more water according to the consistency you prefer.
Add the heavy cream, mix well and switch off the stove. Make sure to keep the pressure cooker away from heat once you have added the heavy cream.