Lay down the bunch of drumstick leaves on a flat surface like a table (you can keep a plastic paper over which you can keep the leaves which will make the clean up later easier).
Gently remove the leaves from the stems. Make sure to remove all thick stems, it is fine to have a few very fine stems.
Transfer the leaves to a large bowl and rinse the leaves using fresh water. It will be quite difficult to drain the water from the bowl, it is more easy to take the leaves with your hands as they will come off easily. Transfer the washed leaves to another clean bowl. Repeat this for two to three times, so you can transfer all the leaves from the water easily.
Grind together the grated coconut, garlic, ginger, cumin seeds and green chili with two cups of water in a food processor, to make a yummy coconut base for the curry.
Transfer the drumstick leaves to the pressure cooker, add the grind coconut mixture and stir well.
Add the red cowpeas, and you can add the remaining 3 cups of water to the pressure cooker.
Add the remaining spices - turmeric powder, red chili powder, garam masala powder and also enough salt to the cooker and mix everything well.
Cover the cooker with lid and safety valve and cook the contents in medium to heat for about 12 minutes or until 3 to 4 whistles come.
After 12 minutes of cooking, switch off the pressure cooker and allow it to cool down.
Once the cooker is cooled enough, open the cooker and see if all the contents including the red cowpeas (vanpayais cooked and soft.
Mix the contents very well, you may add a little more water if you prefer more gravy for the curry (heat the mixture for another 1 to 2 minutes in low heat if you are adding extra water).
Drumstick leaves curry is ready to be served!
Serve the healthy, easy and delicious drumstick leaves curry in coconut gravy along with rice for lunch or dinner.