Black gram is a common name for the edible bean that is taken from the seed pod of the Vigna mungo L. Hepper plant, which is indigenous to the Indian subcontinent. Black gram in its natural form is also referred to as urad bean, or urd. When the bean is purposely removed from its name-giving black skin, or seed coat, it is white in colour and is often referred to as urad dal, or white urad. Skinned black gram is used in various south Indian dishes after it is ground into a white flour or paste.
Place black gram in a large pot and fill with hot tap water that is equivalent to four times the quantity of black gram. If you have 454gr, or 2 cups, of black gram, then add 1814gr, or 8 cups, of hot water to the pot.
Let black gram soak for at least 5 to 6 hours, or even overnight.
Transfer the black gram and water to a pressure cooker and cook for 20 minutes. Remove from the heat and transfer the black gram and water back to the pot and set aside to cool for approximately one hour. Scoop a handful of black gram at a time and rub the seeds gently between the palms of your hands to remove the skin. This will skin the beans and leave them whole. The skins will float on the top of the pot and can be poured out with the water, leaving the heavier beans in the bottom of the pot.
Soak the black gram overnight in the pot if you do not have a pressure cooker. Drain the pot and pour the black gram out onto a towel, spreading the plants in an even layer on a towel. Cover the layer of black gram with another towel and roll your rolling pin back and forth over the length of the top towel. Roll several times, stopping every now and then to lift the towel and check progress of skinning, to see how many skins are left on the beans every couple of rolls. This rolling technique will skin the beans, but also split many of the beans -- as opposed to the pressure cooker method, which will leave the beans whole. Splitting the beans will actually be useful, as many uses of the white interior of the black gram bean will require split or ground beans.
Wash the skinned black gram in two or three changes of water. You are now ready to use the skinned black gram in its whole form, or you may further split the bean, or even grind the beans into a flour or paste.
If you have time constraints, buy already skinned whole or split black gram beans. The process for skinning black gram beans mirrors that of chick peas.