Soak the green moong in plenty of water for 5-6 hours or overnight.
Drain the soaked water and add the green moong to a blender. To this, add sliced ginger and green chillies. Blend this to a fine batter, with the addition of around 1/2 cup water. It is better to have a thick batter that can be thinned as per our requirement while preparing the pesarattu.
Remove this to a bowl. Mix in the salt and rice flour (if using).
Heat a tava or a flat skillet. Brush some oil (I like using gingelly oil, but sunflower or coconut oil or ghee also works well).
Adjust consistency of the batter so it is not too thick and pours well.
Pour 1-2 ladles of batter (depending on the size of the ladle and of the pan) in the centre of the hot tava and keep moving the ladle in concentric circles outwards to make the pesarattu as thick or thin as you want it to be.
Drizzle oil or ghee around the circumference and over the top (around 1 tsp).
Wait for the pesarattu to cook through and turn slightly golden brown.
Flip over and cook for another 10-20 seconds. Some don’t flip and serve it directly which is fine too.
Serve hot with any chutney you like.
Any remaining batter can be refrigerated for 2 days in an airtight container. Bring it to room temperature before using.