Pulse 150 g basmati rice in a blender or food processor until it forms a thick, slightly coarse paste. Scrape into a bowl, pour over enough water to submerge it, and leave to soak overnight.
Submerge 150 g urad dal in water in a separate bowl and leave to soak overnight.
Drain the soaked urad dal and place it into a blender. Add the seeds for the dal paste (3.7 g fenugreek seeds) and blend thoroughly to form a smooth, fine puree.
Fold the pureed urad dal into the soaked rice paste until evenly combined, then set the mixture aside overnight to ferment.
Stir salt to taste into the fermented batter.
Set a large non-stick frying pan, skillet, or flat tawa over medium heat. Spoon a ladle of batter into the centre and spread it outward in a continuous spiral using the underside of the ladle to create an even, paper-thin circle.
Cook for roughly 2 minutes until the surface looks dry, then drizzle ghee or vegetable oil over the centre and around the edges. Continue cooking for another 2 minutes until the underside turns deeply golden and crisp.
Roll the dosa into a cylinder and transfer to a plate. Repeat the cooking process with the remaining batter, serving immediately alongside Nariyal Tamatar ki Chutney and piping hot Sambhar.