In a mixing bowl, combine 507 g plain yogurt, 4 tablespoon chickpea flour, the karhi spices, and salt to taste. Whisk until smooth, then whisk in 1 litre of water and set aside.
Submerge 100 g moong dal in a bowl of fresh water and soak for 2 hours, then drain thoroughly.
Transfer the drained dal to a food processor or blender along with 0.3 g salt and 500 ml water. Process until you achieve a light, airy batter, then scrape into a bowl.
Pour vegetable oil or ghee for deep-frying into a deep, sturdy pot and bring to 180°C (350°F). Drop small spoonfuls of the batter into the hot fat and fry in batches for 2 to 3 minutes until deep golden, then remove with a slotted spoon to drain on paper towels.
Pour the whisked yoghurt mixture into a wide heavy pot and warm over medium heat until it nearly boils. Lower the flame to low, cover, and cook for 5 to 10 minutes, stirring from time to time, until it settles into a thin sauce consistency.
Drop the fried dumplings into the sauce, bring back up to a boil, then lower the heat and simmer gently for 4 to 5 minutes.
While the curry simmers, melt 125 g ghee or vegetable oil in a frying pan over medium heat. Add the tempering spices and fry for 1 to 2 minutes, stirring, until the seeds pop, the asafoetida expands, and the chillies darken.
Pour the sizzling spiced oil directly over the karhi, remove the pot from the heat, and adjust the salt seasoning as needed.
Steep a tiny pinch (0.1 g per 2 g turmeric) in 2 tbsp warm water; use to match the rich golden hue. Contributes an aristocratic, honeyed floral flavour rather than earthy bitterness.
For crisping batters or binding cutlets: use 50% to 60% of the weight. Produces a very crisp shell but lacks the earthy, roasted nutty flavour of besan.
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.
Use the same weight. The seeds are smaller and hotter; fry in hot oil until they pop, about 20–30 seconds, and reduce the heat if they darken too fast. The dish will be a little sharper.
Use 70% of the weight of whole seed, added with the other ground spices rather than fried whole. You lose the popping texture and the heat comes through more evenly.