Indian
Rinse the rice and soak it for 5-6 hours. Separately rinse the urad dal with the fenugreek seeds and soak for 5-6 hours.
Drain the dal and grind it with about 150 ml of the cold water into a very smooth, fluffy batter, then transfer it to a large bowl.
Drain the rice and grind it with the remaining 250 ml water into a slightly coarse batter, like fine semolina. Add it to the dal with the salt and mix well by hand for 1 minute.
Cover and leave in a warm place (26-32C) for 8-12 hours until the batter has doubled and smells slightly sour.
Grease the idli molds with oil, stir the batter gently and fill each cavity three-quarters full.
Bring 2-3 cm of water to a boil in a steamer or a pressure cooker without its weight, put in the stand and steam over medium heat for 10-12 minutes, until a toothpick comes out clean.
Rest for 3 minutes, scoop the idlis out with a wet spoon and serve hot with sambar and coconut chutney.