Soak moong and urad dal separately in warm water overnight or for 6-8 hours.
Drain out the water from both moong and urad dal. Wash them under running water separately using a strainer.
Using ¼ - ⅓ cup grind the urad dal into a fine paste. Remove the paste into a big mixing bowl.
Next add the soaked moong and chopped spinach into the blender jug. Using ½ - ¾ cup of water grind to a coarse paste.
Add the moong spinach paste to the urad dal paste.
Add salt and mix well. Cover the bowl and let the batter ferment for 3 - 4 hours.
Heat oil in a small pan over low to medium heat.
Add mustard seeds, cumin seeds and urad dal to it.
Stir fry till the dal becomes pink in colour.
Add asafoetida, chopped curry leaves and chopped onion. Stir fry for 2-3 minutes.
Add the sprouted moong and mix. Take the pan off the heat. You don't want to cook the sprouted moong.
Add the tempering to the batter.
Add ginger and chilli too. Mix the batter well.
Heat a paniyaram pan over medium to low heat.
Add about 2-3 drops of oil into each cavity or mould.
Add about a tablespoon of the batter into each mould. Filling each mould ¾ of the way is a good guideline.
Cover the lid and let the paniyaram steam for 2-3 minutes.
Take the lid off the pan. If the top part of the paniyaram seems steamed, flip each one over to cook the top side using a spoon or a fork.
Drop into each mould a drop or 2 of oil and let the other side of the paniyaram become golden brown.
Repeat with the remaining batter.
Serve hot moong paniyaram with your favorite chutney and sambar. Can be served alone with some chutney. I served them with ridge gourd chutney.