Cover the whole mung beans in water and soak for 4 hours to over-night.
Blend together the softened beans, ginger, chili, and salt, with half a cup of water. (Plus any additional seasonings as desired.) You should end up with a runny batter that still has a rough texture. Add a few more tablespoons of water, more, or less as needed. The thinner the batter the crispier the pesarattu will be. Leaving the batter to rest for 30 minutes is best practice, but can be skipped if time doesn't allow.
Preheat a heavy skillet or crepe pan well and reduce heat to medium/medium-high. Add a small amount of ghee/better/oil as desired and spread well across the pan.
Pour in batter and spread by tilting the pan or using a spatula, until the entire surface is covered thin and evenly. (This is the time to sprinkle on any add-ins such as chopped onions, chilies, or cilantro.)
In restaurants the cooking surface tends to be very hot eliminating the need to flip the pesarattu, however it is entirely acceptable to flip them when homemade. Either way, you will need to wait until the edges have crisped and are golden before removing from the pan or flipping.
Serve the pesarattu open, folded, or rolled with soft cheese, chutney, sambal, umpa, sambar or other prepared dal as desired.