Submerge 200 g moong dal in a bowl of water and leave to soak for 8 to 10 hours.
Drain the soaked dal thoroughly and blend in a food processor until it forms a very smooth paste. Transfer to a bowl, beat vigorously by hand to incorporate air, and stir in salt to taste.
Add 250 g ginger tomato sauce to a saucepan and place over low heat to warm. Pour 228 g mustard oil into a flat kadhai or wide, heavy frying pan and set over high heat.
Take small portions of the batter and squeeze them between your thumb and index finger directly into the hot oil. Turn down the heat and fry undisturbed for a few minutes until steam bubbles break on the surface, then flip and fry for several minutes more until evenly golden brown.
Transfer the fried dumplings with a slotted spoon directly into the warm ginger tomato sauce. Simmer gently for 10 to 15 minutes, loosening with a splash of water if needed, until piping hot.
Use equal weight. It cooks in about the same time and breaks down to a similar soft, creamy consistency, though the colour will be slightly pinkish-orange.